Material for organic electroluminescence device and organic electroluminescence device

ABSTRACT

A material for organic EL device which includes a compound having a specific structure: an azine ring having a cyano-substituted aromatic hydrocarbon group, an azine ring having a cyano-substituted heterocyclic group, or an azine ring having a cyano group directly bonded to the azine ring. An organic electroluminescence device including an organic thin film layer between a cathode and an anode, wherein the organic thin film layer includes a light emitting layer and at least one layer containing the material for organic electroluminescence device, has a long lifetime.

TECHNICAL FIELD

The present invention relates to materials for organicelectroluminescence devices and organic electroluminescence devicesemploying the materials.

BACKGROUND ART

By applying voltage to an organic electroluminescence device (alsoreferred to as “organic EL device”), holes from an anode and electronsfrom a cathode are injected into a light emitting layer. The holes andelectrons injected into the light emitting layer recombine to formexcitons. The singlet exciton and the triplet exciton are formed at aratio of 25%:75% according to spin-statistics theorem. Since thefluorescence utilizes the emission from singlet excitons, it has beenknown that the internal quantum efficiency of a fluorescent organic ELdevice is limited to 25%. In contrast, since the phosphorescenceutilizes the emission from triplet excitons, it has been known that theinternal quantum efficiency of a phosphorescent organic EL device can beincreased to 100% if the intersystem crossing occurs efficiently.

In the development of known organic EL devices, an optimum device designhas been made depending upon the emission mechanism such as fluorescenceand phosphorescence. It has been known in the art that ahigh-performance phosphorescent organic EL device cannot be obtained bya mere application of the fluorescent technique to the phosphorescentdevice, because the emission mechanisms are different from each other.This may be generally because the following reasons.

Since the phosphorescence utilizes the emission from triplet excitons, acompound with larger energy gap is required to be used in the lightemitting layer. This is because that the singlet energy (energydifference between the lowest excited singlet state and the groundstate) of a compound is generally larger than its triplet energy (energydifference between the lowest excited triplet state and the groundstate).

Therefore, to effectively confine the triplet energy of a phosphorescentdopant material within a device, a host material having triplet energylarger than that of the phosphorescent dopant material should be used inthe light emitting layer. In addition, if an electron transporting layerand a hole transporting layer is formed adjacent to the light emittinglayer, a compound having triplet energy larger than that of thephosphorescent dopant material should be used also in the electrontransporting layer and the hole transporting layer. Thus, the devicedesign conventionally employed for developing a phosphorescent organicEL device results in the use of a compound having an energy gap largerthan that of a compound for use in a fluorescent organic EL device,thereby increasing the voltage for driving an organic EL device.

A hydrocarbon compound highly resistant to oxidation and reduction,which has been known as a useful compound for a fluorescent device, hasa small energy gap because of a broad distribution of n-electron cloud.Therefore, such a hydrocarbon compound is not suitable for use in aphosphorescent organic EL device and, instead, an organic compoundhaving a heteroatom, such as oxygen and nitrogen, has been selected.However, a phosphorescent organic EL device employing such an organiccompound having a heteroatom has a shorter lifetime as compared with afluorescent organic EL device.

In addition, a phosphorescent dopant material has an extremely longerrelaxation time of triplet excitons as compared with that of its singletexcitons, this largely affecting the device performance. Namely, in theemission from singlet excitons, since the relaxation speed which leadsto emission is high, the diffusion of excitons into a layer adjacent tothe light emitting layer (for example, a hole transporting layer and anelectron transporting layer) is difficult to occur and efficientemission is expected. In contrast, the emission from triplet excitons isa spin-forbidden transition and the relaxation speed is low. Therefore,the diffusion of excitons into adjacent layers occurs easily and thethermal energy deactivation occurs in most compounds other than thespecific phosphorescent compound. Thus, as compared with a fluorescentorganic EL device, it is more important for a phosphorescent organic ELdevice to control the region for recombining electrons and holes.

For the above reasons, the development of a high performancephosphorescent organic EL device requires the selection of materials andthe consideration of device design which are different from those for afluorescent organic EL device.

A carbazole derivative having a high triplet energy and a carbazoleskeleton known as a principal skeleton of hole transporting materialshas been conventionally used as a useful phosphorescent host material.

Patent Document 1 describes, as a material for organic EL device, acompound in which a nitrogen-containing heterocyclic group is introducedinto a biscarbazole skeleton which includes two carbazole structuresconnected to each other. The compound described in Patent Document 1 ismolecularly designed to balance the charge transport by introducing anelectron-deficient nitrogen-containing heterocyclic group to a holetransporting carbazole skeleton. Patent Document 2 describes that thecharge injecting ability of a N,N-biscarbazole compound wherein twocarbazole structures are bonded to each other via a biphenyl group isimproved by introducing an electron-withdrawing group into theintervening biphenyl group between two carbazole structures.

However, the improvement of the lifetime of organic EL device is stillrequired and the development of a new material for organic EL devicewhich realizes a longer lifetime has been demanded.

PRIOR ART Patent Documents

-   Patent Document 1: WO 2011/132684-   Patent Document 2: JP 2011-176258

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

An object of the invention is to provide a material for organicelectroluminescence device capable of realizing an organicelectroluminescence device with a longer lifetime and an organicelectroluminescence device employing such a material.

Means for Solving Problem

As a result of extensive research, the inventors have found that amaterial for organic EL device represented by formula (I) realizes anorganic EL device with a lifetime longer than those known in the art andmade the invention based on this finding. The material for organic ELdevice represented by formula (I) has a central skeleton to which anazine ring having a cyano-substituted aromatic hydrocarbon group, anazine ring having a cyano-substituted heterocyclic group, or an azinering having a cyano group directly bonded to the azine ring is bonded ata specific position of the central skeleton.

The present invention provides:

1. A material for organic electroluminescence device represented byformula (I):

wherein

each of A¹ and A² independently represents a single bond, a substitutedor unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms, or a substituted or unsubstituted heterocyclic group having 5 to30 ring atoms;

each of X¹ to X⁸ and Y¹ to Y⁸ independently represents N (nitrogen atom)or CR^(a) (C represents a carbon atom);

each of R^(a) independently represents a hydrogen atom, a substituted orunsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms, a substituted or unsubstituted heterocyclic group having 5 to 30ring atoms, a substituted or unsubstituted alkyl group having 1 to 30carbon atoms, a substituted or unsubstituted silyl group, or a halogenatom, provided that when two or more R^(a) groups exist, the R^(a)groups may be the same or different;

L¹ represents a single bond, a substituted or unsubstituted divalentaromatic hydrocarbon group having 6 to 30 ring carbon atoms, or asubstituted or unsubstituted divalent heterocyclic group having 5 to 30ring atoms;

n represents an integer of 0 to 3, provided that when n=0, L¹ representsa single bond and one of X⁵ to X⁸ and one of Y¹ to Y⁸ and A² aredirectly bonded to each other;

one of X⁵ to X⁸ and one of Y¹ to Y⁸ and A² are bonded to each other viaL¹ or directly;

each of sa and ta independently represents an integer of 0 to 5, each ofsb, tb and tc independently represents an integer of 0 to 4, and screpresents an integer of 0 to 3, provided that sa+sb+sc+ta+tb+tcrepresents an integer of 1 to 5;

when sa is 1 to 5, A¹ and Q¹ of (Q¹)_(sa) are bonded to each other;

when sb is 1 to 4, at least one of X¹ to X⁴ and Q¹ of (Q¹)_(sb) arebonded to each other;

when sc is 1 to 3, at least one of X⁵ to X⁸ and Q¹ of (Q¹)_(sc) arebonded to each other;

when ta is 1 to 5, A² and Q² of (Q²)_(ta) are bonded to each other;

when tb is 1 to 4, at least one of Y⁵ to Y⁸ and Q² of (Q²)_(tb) arebonded to each other;

when tc is 1 to 4, at least one of Y¹ to Y⁴ and Q² of (Q²)_(tc) arebonded to each other;

each of Q¹ and Q² independently represents -Az-W_(q);

q represents an integer of 1 to 4;

when two or more Q¹ groups exist, the Q¹ groups may be the same ordifferent;

when two or more Q² groups exist, the Q² groups may be the same ordifferent;

Az represents a q+1 valent residue of a ring represented by formula (X):

wherein

each of Z¹ to Z⁵ independently represents a nitrogen atom or CR^(b);

R^(b) is as defined in R^(a), provided that when any two of Z¹ to Z⁵adjacent to each other represent CR^(b), the adjacent R^(b) groups maybe bonded to each other to form a ring structure;

when two or more R^(b) groups exist, the R^(b) groups may be the same ordifferent;

when two or more Az groups exist, the Az groups may be the same ordifferent;

W represents a cyano group, a cyano-substituted aromatic hydrocarbongroup having 6 to 30 ring carbon atoms, or a cyano-substitutedheterocyclic group having 5 to 30 ring atoms, provided that thecyano-substituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms and the cyano-substituted heterocyclic group having 5 to 30 ringatoms may be further substituted by a substituent other than a cyanogroup, and

when two or more W groups exist, the W groups may be the same ordifferent;

2. The material for organic electroluminescence device according to item1, represented by formula (II):

wherein

A¹, A², X¹ to X⁸, Y¹ to Y⁸, L¹, n, sa, sb, sc, ta, tb, Q¹, and Q² are asdefined above,

tc represents an integer of 0 to 3, provided that sa+sb+sc+ta+tb+tcrepresents an integer of 1 to 5; and one of X⁵ to X⁸ and one of Y¹ to Y⁴are bonded to each other via L¹ or directly;

3. The material for organic electroluminescence device according to item1 or 2, represented by formula (III):

wherein

A¹, A², X¹ to X⁸, Y¹ to Y⁸, L¹, n, Q¹, and Q² are as defined above;

each of sa and ta independently represents an integer of 0 to 5,provided that sa+ta represents an integer of 1 to 5; and

one of X⁵ to X⁸ and one of Y¹ to Y⁴ are bonded to each other via L¹ ordirectly;

4. The material for organic electroluminescence device according to anyone of items 1 to 3, wherein X⁷ and Y³ are bonded to each other via L¹or directly;

5. The material for organic electroluminescence device according to anyone of items 1 to 3, wherein X⁶ and Y² are bonded to each other via L¹or directly;

6. The material for organic electroluminescence device according to anyone of items 1 to 3, wherein X⁶ and Y³ are bonded to each other via L¹or directly;

7. The material for organic electroluminescence device according to anyone of items 1 to 6, wherein Az represents a q+1 valent residue of aring selected from the group consisting of a substituted orunsubstituted pyrimidine ring, a substituted or unsubstituted triazinering, a substituted or unsubstituted pyridine ring, and a substituted orunsubstituted quinazoline ring;

8. The material for organic electroluminescence device according to anyone of items 1 to 7, wherein L¹ represents a phenylene group and nrepresents an integer of 1 to 3, or L¹ represents a single bond and nrepresents 0;

9. The material for organic electroluminescence device according to anyone of items 1 to 8, wherein W represents a cyano-substituted phenylgroup, a cyano-substituted biphenyl group, a cyano-substituted9,9-diphenylfluorenyl group, a cyano-substituted9,9′-spirobi[9H-fluorene]-2-yl group, a cyano-substituted9,9-dimethylfluorenyl group, a cyano-substituted dibenzofuranyl group,or a cyano-substituted dibenzothiophenyl group;

10. The material for organic electroluminescence device according to anyone of items 1 to 9, wherein each of sa, sb, sc, ta, tb, and tcrepresents 0 or 1;

11. The material for organic electroluminescence device according to anyone of items 1 to 10, wherein each of ta, tb and tc represents 0;

12. The material for organic electroluminescence device according to anyone of items 1 to 11, wherein sa+sb+sc+ta+tb+tc represents 1;

13. The material for organic electroluminescence device according to anyone of items 1 to 12, wherein q represents 1 or 2;

14. The material for organic electroluminescence device according to anyone of items 1 to 13, wherein q represents 1;

15. An organic electroluminescence device comprising an organic thinfilm layer comprising one or more layers between a cathode and an anode,

wherein

the organic thin film layer comprises a light emitting layer, and

at least one layer of the organic thin film layer comprises the materialfor organic electroluminescence device according to any one of items of1 to 14;

16. The organic electroluminescence device according to claim 15,wherein the light emitting layer comprises the material for organicelectroluminescence device;

17. The organic electroluminescence device according to item 15 or 16,wherein the light emitting layer comprises a phosphorescent emittingmaterial selected from ortho metallated complexes of a metal selectedfrom iridium (Ir), osmium (Os), and platinum (Pt);

18. The organic electroluminescence device according to any one of items15 to 17, wherein the light emitting layer comprises a first hostmaterial selected from the material for organic electroluminescencedevice and a second host material represented by formula (1):

wherein

Z¹¹ represents a ring structure fused to a side a and represented byformula (1-1) or (1-2), and Z¹² represents a ring structure fused to aside b and represented by formula (1-1) or (1-2), provided that at leastone of Z¹¹ and Z¹² is represented by formula (1-1):

in formula (1-1),

a side c is fused to the side a or b of formula (1);

in formula (1-2),

any one of sides d, e and f is fused to the side a or b of formula (1);

in formulae (1-1) and (1-2),

X¹¹ represents a sulfur atom, an oxygen atom, N—R¹⁹, or C(R²⁰)(R²¹⁾;

each of R¹¹ to R²¹ independently represents a hydrogen atom, a heavyhydrogen atom, a halogen atom, a cyano group, a substituted orunsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms, a substituted or unsubstituted heterocyclic group having 5 to 30ring atoms, a substituted or unsubstituted alkyl group having 1 to 30carbon atoms, a substituted or unsubstituted alkenyl group having 2 to30 carbon atoms, a substituted or unsubstituted alkynyl group having 2to 30 carbon atoms, a substituted or unsubstituted alkylsilyl grouphaving 3 to 30 carbon atoms, a substituted or unsubstituted arylsilylgroup having 6 to 30 ring carbon atoms, a substituted or unsubstitutedalkoxy group having 1 to 30 carbon atoms, a substituted or unsubstitutedaralkyl group having 6 to 30 ring carbon atoms, or a substituted orunsubstituted aryloxy group having 6 to 30 ring carbon atoms, providedthat adjacent groups of R¹¹ to R²¹ may be bonded to each other to form aring;

M¹ represent a substituted or unsubstituted nitrogen-containing aromaticheteroring having 5 to 30 ring atoms;

L² represents a single bond, a substituted or unsubstituted divalentaromatic hydrocarbon group having 6 to 30 ring carbon atoms, asubstituted or unsubstituted divalent heterocyclic group having 5 to 30ring atoms, a cycloalkylene group having 5 to 30 ring atoms, or a groupin which the preceding groups are directly linked to each other; and

k represents 1 or 2;

19. The organic electroluminescence device according to item 18, whereinthe second host material is represented by formula (2):

wherein

Z¹¹ represents a ring structure fused to the side a and represented byformula (1-1) or (1-2), and Z¹² represents a ring structure fused to theside b and represented by formula (1-1) or (1-2), provided that at leastone of Z¹¹ and Z¹² is represented by formula (1-1);

L² is as defined in formula (1);

each of X¹² to X¹⁴ independently represents a nitrogen atom, CH, or acarbon atom bonded to R³¹ or L², provided that at least one of X¹² toX¹⁴ represents a nitrogen atom;

each of Y¹¹ to Y¹³ independently represents CH or a carbon atom bondedto R³¹ or L²;

each of R³¹ independently represents a halogen atom, a cyano group, asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 30ring carbon atoms, a substituted or unsubstituted heterocyclic grouphaving 5 to 30 ring atoms, a substituted or unsubstituted alkyl grouphaving 1 to 30 carbon atoms, a substituted or unsubstituted alkenylgroup having 2 to 30 carbon atoms, a substituted or unsubstitutedalkynyl group having 2 to 30 carbon atoms, a substituted orunsubstituted alkylsilyl group having 3 to 30 carbon atoms, asubstituted or unsubstituted arylsilyl group having 6 to 30 ring carbonatoms, a substituted or unsubstituted alkoxy group having 1 to 30 carbonatoms, a substituted or unsubstituted aralkyl group having 6 to 30 ringcarbon atoms, or a substituted or unsubstituted aryloxy group having 6to 30 ring carbon atoms;

when two or more R³¹ groups exist, the R³¹ groups may be the same ordifferent and adjacent R³¹ groups may be bonded to each other to form aring;

k represents 1 or 2, and m represents an integer of 0 to 4;

the side c of formula (1-1) is fused to the side a or b of formula (2);and

any one of sides d, e and f of formula (1-2) is fused to the side a or bof formula (2);

20. The organic electroluminescence device according to item 18 or 19,wherein the second host material is represented by formula (3):

wherein

L² is as defined in formula (1);

each of X¹² to X¹⁴ independently represents a nitrogen atom, CH, or acarbon atom bonded to R³¹ or L², provided that at least one of X¹² toX¹⁴ represents a nitrogen atom;

each of Y¹¹ to Y¹³ independently represents CH or a carbon atom bondedto R³¹ or L²;

each of R³¹ independently represents a halogen atom, a cyano group, asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 30ring carbon atoms, a substituted or unsubstituted heterocyclic grouphaving 5 to 30 ring atoms, a substituted or unsubstituted alkyl grouphaving 1 to 30 carbon atoms, a substituted or unsubstituted alkenylgroup having 2 to 30 carbon atoms, a substituted or unsubstitutedalkynyl group having 2 to 30 carbon atoms, a substituted orunsubstituted alkylsilyl group having 3 to 30 carbon atoms, asubstituted or unsubstituted arylsilyl group having 6 to 30 ring carbonatoms, a substituted or unsubstituted alkoxy group having 1 to 30 carbonatoms, a substituted or unsubstituted aralkyl group having 6 to 30 ringcarbon atoms, or a substituted or unsubstituted aryloxy group having 6to 30 ring carbon atoms;

when two or more R³¹ groups exist, the R³¹ groups may be the same ordifferent and adjacent R³¹ groups may be bonded to each other to form aring;

m represents an integer of 0 to 4;

each of R⁴¹ to R⁴⁸ independently represents a hydrogen atom, a heavyhydrogen atom, a halogen atom, a cyano group, a substituted orunsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms, a substituted or unsubstituted heterocyclic group having 5 to 30ring atoms, a substituted or unsubstituted alkyl group having 1 to 30carbon atoms, a substituted or unsubstituted alkenyl group having 2 to30 carbon atoms, a substituted or unsubstituted alkynyl group having 2to 30 carbon atoms, a substituted or unsubstituted alkylsilyl grouphaving 3 to 30 carbon atoms, a substituted or unsubstituted arylsilylgroup having 6 to 30 ring carbon atoms, a substituted or unsubstitutedalkoxy group having 1 to 30 carbon atoms, a substituted or unsubstitutedaralkyl group having 6 to 30 ring carbon atoms, or a substituted orunsubstituted aryloxy group having 6 to 30 ring carbon atoms; and

adjacent groups of R⁴¹ to R⁴⁸ may be bonded to each other to form aring;

21. The organic electroluminescence device according to any one of items18 to 20, wherein the second host material is represented by formula(4):

wherein

L² is as defined in formula (1);

each of X¹² to X¹⁴ independently represents a nitrogen atom, CH, or acarbon atom bonded to R³¹ or L², provided that at least one of X¹² toX¹⁴ represents a nitrogen atom;

each of Y¹¹ to Y¹³ independently represents CH or a carbon atom bondedto R³¹ or L²;

each of R³¹ independently represents a halogen atom, a cyano group, asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 30ring carbon atoms, a substituted or unsubstituted heterocyclic grouphaving 5 to 30 ring atoms, a substituted or unsubstituted alkyl grouphaving 1 to 30 carbon atoms, a substituted or unsubstituted alkenylgroup having 2 to 30 carbon atoms, a substituted or unsubstitutedalkynyl group having 2 to 30 carbon atoms, a substituted orunsubstituted alkylsilyl group having 3 to 30 carbon atoms, asubstituted or unsubstituted arylsilyl group having 6 to 30 ring carbonatoms, a substituted or unsubstituted alkoxy group having 1 to 30 carbonatoms, a substituted or unsubstituted aralkyl group having 6 to 30 ringcarbon atoms, or a substituted or unsubstituted aryloxy group having 6to 30 ring carbon atoms;

when two or more R³¹ groups exist, the R³¹ groups may be the same ordifferent and adjacent R³¹ groups may be bonded to each other to form aring;

m represents an integer of 0 to 4;

each of L³ and L⁴ independently represents a single bond, a substitutedor unsubstituted divalent aromatic hydrocarbon group having 6 to 30 ringcarbon atoms, a substituted or unsubstituted divalent heterocyclic grouphaving 5 to 30 ring atoms, a cycloalkylene group having 5 to 30 ringatoms, or a group in which the preceding groups are directly linked toeach other;

each of R⁵¹ to R⁵⁴ independently represents a halogen atom, a cyanogroup, a substituted or unsubstituted aromatic hydrocarbon group having6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclicgroup having 5 to 30 ring atoms, a substituted or unsubstituted alkylgroup having 1 to 30 carbon atoms, a substituted or unsubstitutedalkenyl group having 2 to 30 carbon atoms, a substituted orunsubstituted alkynyl group having 2 to 30 carbon atoms, a substitutedor unsubstituted alkylsilyl group having 3 to 30 carbon atoms, asubstituted or unsubstituted arylsilyl group having 6 to 30 ring carbonatoms, a substituted or unsubstituted alkoxy group having 1 to 30 carbonatoms, a substituted or unsubstituted aralkyl group having 6 to 30 ringcarbon atoms, or a substituted or unsubstituted aryloxy group having 6to 30 ring carbon atoms;

when two or more R⁵¹ groups exist, the R⁵¹ groups may be the same ordifferent and adjacent R⁵¹ groups may be bonded to each other to form aring;

when two or more R⁵² groups exist, the R⁵² groups may be the same ordifferent and adjacent R⁵² groups may be bonded to each other to form aring;

when two or more R⁵³ groups exist, the R⁵³ groups may be the same ordifferent and adjacent R⁵³ groups may be bonded to each other to form aring;

when two or more R⁵⁴ groups exist, the R⁵⁴ groups may be the same ordifferent and adjacent R⁵⁴ groups may be bonded to each other to form aring;

M² represents a substituted or unsubstituted aromatic hydrocarbon grouphaving 6 to 30 ring carbon atoms or a substituted or unsubstitutedheterocyclic group having 5 to 30 ring atoms; and

each of p and s independently represents an integer of 0 to 4, and eachof q and r independently represents an integer of 0 to 3; and

22. The organic electroluminescence device according to any one of items15 to 17, wherein the light emitting layer comprises a first hostmaterial selected from the materials for organic electroluminescencedevice and a second host material selected from compounds having nocyano group.

EFFECT OF THE INVENTION

According to the present invention, an organic electroluminescencedevice having a long lifetime and a material for organicelectroluminescence device realizing such an organic electroluminescencedevice are provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view of an example of the organicEL device of the invention.

MODE FOR CARRYING OUT THE INVENTION

Material for Organic Electroluminescence Device

In an embodiment of the invention, the material for organicelectroluminescence device (hereinafter also referred to as “materialfor organic EL device”) is represented by formula (I);

wherein

each of A¹ and A² independently represents a single bond, a substitutedor unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms, or a substituted or unsubstituted heterocyclic group having 5 to30 ring atoms;

each of X¹ to X⁸ and Y¹ to Y⁸ independently represents N (nitrogen atom)or CR^(a) (C represents a carbon atom);

each of R^(a) independently represents a hydrogen atom, a substituted orunsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms, a substituted or unsubstituted heterocyclic group having 5 to 30ring atoms, a substituted or unsubstituted alkyl group having 1 to 30carbon atoms, a substituted or unsubstituted silyl group, or a halogenatom, provided that when two or more R^(a) groups exist, the R^(a)groups may be the same or different;

L¹ represents a single bond, a substituted or unsubstituted divalentaromatic hydrocarbon group having 6 to 30 ring carbon atoms, or asubstituted or unsubstituted divalent heterocyclic group having 5 to 30ring atoms;

n represents an integer of 0 to 3, provided that when n=0, L¹ representsa single bond and one of X⁵ to X⁸ and one of Y¹ to Y⁸ and A² aredirectly bonded to each other;

one of X⁵ to X⁸ and one of Y¹ to Y⁸ and A² are bonded to each other viaL¹ or directly;

each of sa and ta independently represents an integer of 0 to 5, each ofsb, tb and tc independently represents an integer of 0 to 4, and screpresents an integer of 0 to 3, provided that sa+sb+sc+ta+tb+tcrepresents an integer of 1 to 5;

when sa is 1 to 5, A¹ and Q¹ of (Q¹)_(sa) are bonded to each other;

when sb is 1 to 4, at least one of X¹ to X⁴ and Q¹ of (Q¹)_(sb) arebonded to each other;

when sc is 1 to 3, at least one of X⁵ to X⁸ and Q¹ of (Q¹)_(sc) arebonded to each other;

when ta is 1 to 5, A² and Q² of (Q²)_(ta) are bonded to each other;

when tb is 1 to 4, at least one of Y⁵ to Y⁸ and Q² of (Q²)_(tb) arebonded to each other;

when tc is 1 to 4, at least one of Y¹ to Y⁴ and Q² of (Q²)_(tc) arebonded to each other;

each of Q¹ and Q² independently represents -Az-W_(q);

q represents an integer of 1 to 4;

when two or more Q¹ groups exist, the Q¹ groups may be the same ordifferent;

when two or more Q² groups exist, the Q² groups may be the same ordifferent;

Az represents a q+1 valent residue of a ring represented by formula (X):

wherein

each of Z¹ to Z⁵ independently represents a nitrogen atom or CR^(b);

R^(b) is as defined in R^(a), provided that when any two of Z¹ to Z⁵adjacent to each other represent CR^(b), the adjacent R^(b) groups maybe bonded to each other to form a ring structure;

when two or more R^(b) groups exist, the R^(b) groups may be the same ordifferent;

when two or more Az groups exist, the Az groups may be the same ordifferent;

W represents a cyano group, a cyano-substituted aromatic hydrocarbongroup having 6 to 30 ring carbon atoms, or a cyano-substitutedheterocyclic group having 5 to 30 ring atoms, provided that thecyano-substituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms and the cyano-substituted heterocyclic group having 5 to 30 ringatoms may be further substituted by a substituent other than a cyanogroup, and

when two or more W groups exist, the W groups may be the same ordifferent.

The material for organic EL device represented by formula (I) ispreferably represented by formula (II):

wherein

A¹, A², X¹ to X⁸, Y¹ to Y⁸, L¹, n, sa, sb, sc, ta, tb, Q¹, and Q² are asdefined above;

tc represents an integer of 0 to 3, provided that sa+sb+sc+ta+tb+tcrepresents an integer of 1 to 5; and

one of X⁵ to X⁸ and one of Y¹ to Y⁴ are bonded to each other via L¹ ordirectly.

The bonding between one of X⁵ to X⁸ and one of Y¹ to Y⁴ via L¹ ordirectly is represented, for example, by X⁶-(L¹)_(n)-Y³, X⁶-(L¹)_(n)-Y²,X⁶-(L¹)_(n)-Y¹, X⁶-(L¹)_(n)-Y⁴, X⁷-(L¹)_(n)-Y³, X⁷-(L¹)_(n)-Y²,X⁷-(L¹)_(n)-Y¹, X⁷-(L¹)_(n)-Y⁴, X⁵-(L¹)_(n)-Y³, X⁵-(L¹)_(n)-Y²,X⁵-(L¹)-Y¹, X⁵-(L¹)_(n)-Y⁴, X⁸-(L¹)_(n)-Y³, X⁸-(L¹)_(n)-Y²,X⁸-(L¹)_(n)-Y¹, and X⁸-(L¹)_(n)-Y⁴.

The material for organic EL device represented by formula (I) is morepreferably represented by formula (II-1):

wherein

A¹, A², X¹ to X⁸, Y¹ to Y⁸, L¹, n, sa, sb, ta, tb, Q¹, and Q² are asdefined above; and

one of X⁵ to X⁸ and one of Y¹ to Y⁴ are bonded to each other via L¹ ordirectly.

The material for organic EL device represented by formula (1) is stillmore preferably represented by formula (III);

wherein

A¹, A², X¹ to X⁸, Y¹ to Y⁸, L¹, n, Q¹, and Q² are as defined above; eachof sa and ta independently represents an integer of 0 to 5, providedthat sa+ta represents an integer of 1 to 5; and

one of X⁵ to X⁸ and one of Y¹ to Y⁴ are bonded to each other via L¹ ordirectly.

In a preferred embodiment of formulae (I) to (III), X⁷ and Y³ are bondedto each other via L¹ or directly, X⁶ and Y² are bonded to each other viaL¹ or directly, or X⁶ and Y³ are bonded to each other via L¹- ordirectly. For example, the compounds represented by formulae (I) to(III) are preferably represented by formulae (I-1) to (I-3):

wherein

A¹, A², X¹ to X⁸, Y¹ to Y⁸, L¹, n, sa, sb, sc, ta, tb, tc, Q¹, and Q²are as defined in formula (II).

Each group in formulae (I) to (III), (II-1), and (I-1) to (I-3) isdescribed below in detail.

The aromatic hydrocarbon group having 6 to 30, preferably 6 to 14 ringcarbon atoms represented by A¹, A², R^(a), and R^(b) may be anon-condensed aromatic hydrocarbon group or a condensed aromatichydrocarbon group. Specific examples thereof include phenyl group,naphthyl group, phenanthryl group, biphenyl group, terphenyl group,quaterphenyl group, fluoranthenyl group, triphenylenyl group,phenanthrenyl group, fluorenyl group, spirofluorenyl group,9,9-diphenylfluorenyl group, 9,9′-spirobi[9H-fluorene]-2-yl group,9,9-dimethylfluorenyl group, benzo[c]phenanthrenyl group,benzo[c]triphenylenyl group, naphtho[1,2-c]phenanthrenyl group,naphtho[1,2-a]triphenylenyl group, dibenzo[a,c]triphenylenyl group, andbenzo[b]fluoranthenyl group, with phenyl group, naphthyl group, biphenylgroup, terphenyl group, phenanthryl group, triphenylenyl group,fluorenyl group, spirobifluorenyl group, and fluoranthenyl group beingpreferred.

Examples of the divalent aromatic hydrocarbon group having 6 to 30 ringcarbon atoms represented by L¹ include divalent residues of the aromatichydrocarbon groups represented by A¹, A², R^(a), and R^(b), withphenylene group, biphenylene group, and naphthylene group beingpreferred.

The heterocyclic group having 5 to 30, preferably 5 to 14 ring atomsrepresented by A¹, A², R^(a) and R^(b) may be a non-condensedheterocyclic group or a condensed heterocyclic group. Specific examplesthereof include the residues of pyrrole ring, isoindole ring, benzofuranring, isobenzofuran ring, dibenzothiophene ring, isoquinoline ring,quinoxaline ring, phenanthridine ring, phenanthroline ring, pyridinering, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring,indole ring, quinoline ring, acridine ring, pyrrolidine ring, dioxanering, piperidine ring, morpholine ring, piperazine ring, carbazole ring,furan ring, thiophene ring, oxazole ring, oxadiazole ring, benzoxazolering, thiazole ring, thiadiazole ring, benzothiazole ring, triazolering, imidazole ring, benzimidazole ring, pyran ring, dibenzofuran ring,and benzo[c]dibenzofuran ring, and the residues of derivatives of theserings, with the residues of dibenzofuran ring, carbazole ring,dibenzothiophene ring, and derivatives of these rings being preferred.

Examples of the divalent heterocyclic group having 5 to 30 ring atomsrepresented by L¹ include divalent residues of the heterocyclic groupsrepresented by A¹, A², R^(a), and R^(b), with dibenzofuranylene groupand dibenzothiophenylene group being preferred.

Examples of the alkyl group having 1 to 30, preferably 1 to 6 carbonatoms represented by R^(a) and R^(b) include methyl group, ethyl group,n-propyl group, isopropyl group, n-butyl group, s-butyl group, isobutylgroup, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group,n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecylgroup, n-tridecyl group, n-tetradecyl group, n-pentadecyl group,n-hexadecyl group, n-heptadecyl group, n-octadecyl group, neopentylgroup, 1-methylpentyl group, cyclopropyl group, cyclobutyl group,cyclopentyl group, cyclohexyl group, cyclooctyl group, and adamantylgroup, with methyl group, ethyl group, n-propyl group, isopropyl group,n-butyl group, s-butyl group, isobutyl group, t-butyl group, cyclopentylgroup, and cyclohexyl group being preferred.

Examples of the substituted or unsubstituted silyl group represented byR^(a) and R^(b) include trimethylsilyl group, triethylsilyl group,tributylsilyl group, dimethylethylsilyl group, t-butyldimethylsilylgroup, vinyldimethylsilyl group, propyldimethylsilyl group,dimethylisopropylsilyl group, dimethylpropylsilyl group,dimethylbutylsilyl group, dimethyltertiarybutylsilyl group,diethylisopropylsilyl group, phenyldimethylsilyl group,diphenylmethylsilyl group, diphenyltertiarybutylsilyl group, andtriphenylsilyl group, with trimethylsilyl group, triethylsilyl group,t-butyldimethylsilyl group, vinyldimethylsilyl group, andpropyldimethylsilyl group being preferred.

Examples of the halogen atom represented by R^(a) and R^(b) includefluorine, chlorine, bromine, and iodine, with fluorine being preferred.

When sa and/or ta is 1 or more, each of A¹ and A² is preferably selectedso as to balance the carrier transporting abilities of the compound.Such a selection of A¹ and A² is also effective when the compound of theinvention is used in the light emitting layer as the host material.

Each of A¹ and A² is preferably a single bond or a substituted orunsubstituted phenyl group, more preferably a single bond or a phenylgroup.

Examples of the optional substituent indicated by “substituted orunsubstituted” referred to above or hereinafter include a halogen atom(fluorine, chlorine, bromine, iodine), a cyano group, an alkyl grouphaving 1 to 20, preferably 1 to 6 carbon atoms, a cycloalkyl grouphaving 3 to 20, preferably 5 to 12 carbon atoms, an alkoxyl group having1 to 20, preferably 1 to 5 carbon atoms, a haloalkyl group having 1 to20, preferably 1 to 5 carbon atoms, a haloalkoxyl group having 1 to 20,preferably 1 to 5 carbon atoms, an alkylsilyl group having 1 to 10,preferably 1 to 5 carbon atoms, an aryl group having 6 to 30, preferably6 to 18 ring carbon atoms, an aryloxy group having 6 to 30, preferably 6to 18 ring carbon atoms, an arylsilyl group having 6 to 30, preferably 6to 18 carbon atoms, an aralkyl group having 7 to 30, preferably 7 to 20carbon atoms, and a heteroaryl group having 5 to 30, preferably 5 to 18ring atoms. Examples thereof include those as mentioned above withrespect to R^(a), with a fluorine atom, an alkyl group, a cycloalkylgroup, an alkylsilyl group, an aryl group (aromatic hydrocarbon group),and a heteroaryl group (heterocyclic group) being particularlypreferred.

The carbon number of a to b in the expression of “a substituted orunsubstituted XX group having a to b carbon atoms” is the carbon numberof the unsubstituted XX group and does not include the carbon atom ofthe optional substituent.

The hydrogen atom referred to herein includes isotopes different fromneutron numbers, i.e., light hydrogen (protium), heavy hydrogen(deuterium) and tritium.

Each of Q¹ and Q² independently represents -Az-W_(q),

wherein

q represents an integer of 1 to 4;

Az represents a q+1 valent residue of a ring represented by formula (X);and

W represents a cyano group, a cyano-substituted aromatic hydrocarbongroup having 6 to 30 ring carbon atoms, or a cyano-substitutedheterocyclic group having 5 to 30 ring atoms, provided that thecyano-substituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms and the cyano-substituted heterocyclic group having 5 to 30 ringatoms may be further substituted by a substituent other than a cyanogroup. When two or more W groups exist, the W groups may be the same ordifferent.

In formula (X), R^(b) groups of adjacent CR^(b) groups may be bonded toeach other to form a ring structure. Examples of such a ring structureinclude those corresponding to the aromatic hydrocarbon groups and theheterocyclic groups as mentioned above with respect to A¹, A², R^(a),and Rb.

Examples of the q+1 valent residue of the ring represented by formula(X) for Az include q+1 valent residues of isoquinoline ring, quinoxalinering, phenanthridine ring, phenanthroline ring, pyridine ring, pyrazinering, pyrimidine ring, pyridazine ring, triazine ring, quinazoline ring,quinoline ring, and acridine ring. These rings may be substituted orunsubstituted. Preferred are q+1 valent residues of pyrimidine ring,triazine ring, pyridine ring, quinazoline ring, and phenanthroline ring.

Az is particularly preferably a q+1 valent residue of a substituted orunsubstituted pyrimidine ring, a substituted or unsubstituted triazinering, a substituted or unsubstituted pyridine ring, or a substituted orunsubstituted quinazoline ring.

The substituent for the ring represented by formula (X) is preferably analkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30carbon atoms, a haloalkyl group having 1 to 30 carbon atoms, ahaloalkoxy group, a silyl group, an aromatic hydrocarbon group having 6to 30 ring carbon atoms, or a heterocyclic group having 5 to 30 ringatoms.

Examples of the alkyl group, silyl group, aromatic hydrocarbon group,and heterocyclic group include those as mentioned above with respect toA¹, A², R^(a) and R^(b).

Examples of the haloalkyl group include the alkyl groups mentioned abovewherein at least one hydrogen atom is substituted by a halogen atom,preferably a fluorine atom. Preferred are trifluoromethyl group and2,2-trifluoroethyl group.

Examples of the alkoxy group include methoxy group, propoxy group,pentyloxy group, and hexyloxy group. Examples of the haloalkoxy groupinclude the alkoxy groups mentioned above wherein at least one hydrogenatom is substituted by a halogen atom, preferably a fluorine atom.

Examples of Q¹ and Q² are shown below.

In the above formulae, R represents a substituent and is defined asmentioned above with respect to R^(a) and R^(b). When two or more Rgroups exist, the R groups may be the same or different. R is preferablya substituted or unsubstituted phenyl group, a substituted orunsubstituted biphenyl group, a substituted or unsubstituted fluorenylgroup, a substituted or unsubstituted naphthyl group, a substituted orunsubstituted dibenzofuranyl group, or a substituted or unsubstitutedthiophenyl group.

W is as defined above and p represents an integer of 1 to 5.

W is preferably an aromatic hydrocarbon group having 6 to 30 ring carbonatoms substituted with one or more (preferably 1 to 5, more preferably 1to 2, and still more preferably one) cyano groups or a heterocyclicgroup having 5 to 30 ring atoms substituted with one or more (preferably1 to 5, more preferably 1 to 2, and still more preferably one) cyanogroups, provided that the aromatic hydrocarbon group having 6 to 30 ringcarbon atoms and the heterocyclic group having 5 to 30 ring atoms may befurther substituted with a substituent other than the cyano group.

Examples of the cyano-substituted aromatic hydrocarbon group having 6 to30 ring carbon atoms and the cyano-substituted heterocyclic group having5 to 30 ring atoms for W include a cyano-substituted phenyl group, acyano-substituted biphenyl group, a cyano-substituted naphthyl group, acyano-substituted phenanthryl group, a cyano-substituted9,9-diphenylfluorenyl group, a cyano-substituted9,9′-spirobi[9H-fluorene]-2-yl group, a cyano-substituted9,9-dimethylfluorenyl group, a cyano-substituted dibenzofuranyl group, acyano-substituted dibenzothiophenyl group, a cyano-substitutedtriphenylenyl group, a cyano-substituted dibenzothiophenyl group, acyano-substituted dibenzothiophenyl group, and a cyano-substituteddibenzofuranyl group.

W is preferably a cyano-substituted phenyl group, a cyano-substitutedbiphenyl group, a cyano-substituted 9,9-diphenylfluorenyl group, acyano-substituted 9,9′-spirobi[9H-fluorene]-2-yl group, acyano-substituted 9,9-dimethylfluorenyl group, a cyano-substituteddibenzofuranyl group, a cyano-substituted dibenzothiophenyl group, or acyano group, and more preferably a cyano-substituted phenyl group, acyano-substituted biphenyl group, such as 4-cyanobiphenyl group,3-cyanobiphenyl group, and 2-cyanobiphenyl group, a cyano-substituted9,9-diphenylfluorenyl group, a cyano-substituted9,9′-spirobi[9H-fluorene]-2-yl group, a cyano-substituted9,9-dimethylfluorenyl group, a cyano-substituted dibenzofuranyl group,or a cyano-substituted dibenzothiophenyl group.

When W is a cyano-substituted phenyl group, a cyano-substituted biphenylgroup, or a cyano-substituted fluorenyl group, the triplet energy(energy difference between the lowest excited triplet state and theground state) tends to be larger, as compared when W is a cyano group.Therefore, the emission efficiency is increased by using the compound inthe light emitting layer of organic electroluminescence device, allowingobtaining a more preferred result.

Examples of the substituent other than the cyano group of thecyano-substituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms and the cyano-substituted heterocyclic group having 5 to 30 ringatoms for W include those described above with respect to the optionalsubstituent referred to by “substituted or unsubstituted.”

L¹ preferably represents a single bond, a substituted or unsubstituteddivalent monocyclic hydrocarbon group having 6 ring carbon atoms, or asubstituted or unsubstituted divalent hetero monocyclic group having 6or less ring atoms. With such L¹, the distortion between the ringsrepresented by formula (a) and (b) (for example, carbazole rings andazacarbazole rings, which may be collectively referred to as “carbazolederivative”) is minimized to make it easy to retain the conjugation ofπ-electrons. This allows HOMO (highest occupied molecular orbital) toextend throughout the whole biscarbazole skeleton formed by twocarbazole derivatives, thereby to retain the hole injecting/transportingability of the carbazole skeleton. In more preferred embodiment, L¹ is aphenylene group (n=1 to 3) or a single bond (n=0).

Each of sa, sb, sc, ta, tb, and tc is preferably 0 or 1, each of ta, tband tc is more preferably 0.

The sum of sa+sb+sc+ta+tb+tc is preferably 1.

In addition, q is preferably 1 or 2 and more preferably 1. When q is 1or 2, the energy levels of LUMO and HOMO of the material for organic ELdevice are well balanced, thereby enhancing the emission efficiency ofthe organic EL device employing the material for organic EL device.

In an embodiment of the invention, the material for organic EL devicecomprises a hole transporting biscarbazole skeleton into which anelectron transporting unit Q¹ and/or Q² (cyano group-containing azinering) is introduced. Q¹ and/or Q² is represented by -Az-W_(q), wherein acyano-substituted aromatic hydrocarbon group, a cyano-substitutedheterocyclic group, or a cyano group is introduced into the azine ringAz. Therefore, the carrier balance in the molecule is good and thelifetime of an organic EL device employing the material is prolonged.

As shown in formulae (II-1) and (III), in an embodiment of the materialfor organic EL device of the invention, the electron transporting unitQ¹ and/or Q² is preferably introduced into the terminal end of thebiscarbazole skeleton. When introduced into the terminal end of thebiscarbazole skeleton, the distribution of HOMO (distribution of πelectron cloud) of the biscarbazole skeleton which acts as a holetransporting unit is kept broad, thereby allowing the biscarbazoleskeleton to have a good hole transporting ability. In addition, the holeinjecting/transporting carbazole skeleton and the electroninjecting/transporting cyano group-containing group do not counteracteach other's properties. Therefore, the carrier balance in the moleculeis good and the lifetime of an organic EL device employing the materialis prolonged.

In contrast, in the compound described in Patent Document 2, thedistribution of HOMO on the biscarbazole skeleton is narrowed todecrease the hole transporting ability, because the electron-acceptingcyano group is introduced into the linking group between two carbazolestructures. Therefore, as compared with the material for organic ELdevice of the invention, the compound described in Patent Document 2tends to lose the carrier balance in its molecule.

As compared with the nitrogen-containing heteroring having no cyanogroup, such as the pyrimidine ring and triazine ring described in PatentDocument 1, the azine ring derivatives Q¹ and Q² having anelectron-accepting cyano group is more resistant to holes, although thecyano group-containing azine ring is an electron injecting/transportingring. Therefore, as compared with the organic EL device which employsthe compound described in Patent Document 1, the organic EL device whichemploys the inventive material for organic EL device having the cyanogroup-containing azine ring has a longer lifetime.

In an embodiment of the present invention, the production method of thematerial for organic EL device is not particularly limited and it isproduced according to a known method, for example, by a couplingreaction of a carbazole derivative and an aromatic halogenated compoundin the presence of a copper catalyst described in Tetrahedron 40 (1984)1435 to 1456 or a palladium catalyst described in Journal of AmericanChemical Society 123 (2001) 7727 to 7729.

Specific examples of the material for organic EL device of the inventionare shown below, although not limited thereto.

Organic EL Device

The embodiments of the organic EL device of the invention are describedbelow.

In an embodiment of the invention, the organic EL device comprises anorganic thin film layer between a cathode and an anode. The organic thinfilm layer includes a light emitting layer. By using the material fororganic EL device of the invention in at least one layer of the organicthin film layer, the lifetime of the organic EL device is prolonged.

The material for organic EL device of the invention may be used in anorganic thin film layer, such as a hole transporting layer, a lightemitting layer, an electron transporting layer, a space layer, and ablocking layer, although not limited thereto. The material for organicEL device of the invention is preferably used in a light emitting layerand particularly preferably in a light emitting layer as a hostmaterial. The light emitting layer preferably further comprises afluorescent emitting material or a phosphorescent emitting material,particularly preferably a phosphorescent emitting material. The materialfor organic EL device of the invention is useful as a material for ablocking layer.

The organic EL device of the invention may be any of a single coloremitting device of fluorescent or phosphorescent type, a white-emittingdevice of fluorescent-phosphorescent hybrid type, an emitting device ofa simple type having a single emission unit, and an emitting device of atandem type having two or more emission units, with the phosphorescentdevice being preferred. The “emission unit” referred to herein is thesmallest unit for emitting light by the recombination of injected holesand injected electrons, which comprises one or more organic layerswherein at least one layer is a light emitting layer.

Representative device structures of the simple-type organic EL deviceare shown below.

(1) Anode/Emission Unit/Cathode

The emission unit may be a laminate comprising two or more layersselected from a phosphorescent light emitting layer and a fluorescentlight emitting layer. A space layer may be disposed between the lightemitting layers to prevent the diffusion of excitons generated in thephosphorescent light emitting layer into the fluorescent light emittinglayer. Representative layered structures of the emission unit are shownbelow.

(a) hole transporting layer/light emitting layer (/electron transportinglayer);

(b) hole transporting layer/first phosphorescent light emittinglayer/second phosphorescent light emitting layer (/electron transportinglayer);

(c) hole transporting layer/phosphorescent light emitting layer/spacelayer/fluorescent light emitting layer (/electron transporting layer);

(d) hole transporting layer/first phosphorescent light emittinglayer/second phosphorescent light emitting layer/space layer/fluorescentlight emitting layer (/electron transporting layer);

(e) hole transporting layer/first phosphorescent light emittinglayer/space layer/second phosphorescent light emitting layer/spacelayer/fluorescent light emitting layer (/electron transporting layer);

(f) hole transporting layer/phosphorescent light emitting layer/spacelayer/first fluorescent light emitting layer/second fluorescent lightemitting layer (/electron transporting layer);

(g) hole transporting layer/electron blocking layer/light emitting layer(/electron transporting layer);

(h) hole transporting layer/light emitting layer/hole blocking layer(/electron transporting layer); and

(i) hole transporting layer/fluorescent light emitting layer/tripletblocking layer (/electron transporting layer).

The emission color of the phosphorescent light emitting layer and thatof the fluorescent light emitting layer may be different. For example,the layered structure of the laminated light emitting layer (d) may behole transporting layer/first phosphorescent light emitting layer (redemission)/second phosphorescent light emitting layer (greenemission)/space layer/fluorescent light emitting layer (blueemission)/electron transporting layer.

An electron blocking layer may be disposed between the light emittinglayer and the hole transporting layer or between the light emittinglayer and the space layer, if necessary. Also, a hole blocking layer maybe disposed between the light emitting layer and the electrontransporting layer, if necessary. With such a electron blocking layer ora hole blocking layer, electrons and holes are confined in the lightemitting layer to increase the degree of charge recombination in thelight emitting layer, thereby improving the lifetime.

Representative device structure of the tandem-type organic EL device isshown below.

(2) anode/first emission unit/intermediate layer/second emissionunit/cathode

The layered structure of the first emission unit and the second emissionunit may be selected from those described above with respect to theemission unit.

Generally, the intermediate layer is also called an intermediateelectrode, an intermediate conductive layer, a charge generation layer,an electron withdrawing layer, a connecting layer, or an intermediateinsulating layer. The intermediate layer may be formed by knownmaterials so as to supply electrons to the first emission unit and holesto the second emission unit.

A schematic structure of an example of the organic EL device of theinvention is shown in FIG. 1 wherein the organic EL device 1 isconstructed by a substrate 2, an anode 3, a cathode 4, and an emissionunit 10 disposed between the anode 3 and the cathode 4. The emissionunit 10 includes a light emitting layer 5 which comprises at least onephosphorescent emitting layer containing a phosphorescent host materialand a phosphorescent dopant material. A hole injecting/transportinglayer 6, etc. may be disposed between the light emitting layer 5 and theanode 3, and an electron injecting/transporting layer 7, etc. may bedisposed between the light emitting layer 5 and the cathode 4. Anelectron blocking layer may be disposed on the anode 3 side of the lightemitting layer 5, and a hole blocking layer may be disposed on thecathode 4 side of the light emitting layer 5. With these blockinglayers, electrons and holes are confined in the light emitting layer 5to increase the degree of exciton generation in the light emitting layer5.

In the present invention, the host is referred to as a fluorescent hostwhen combinedly used with a fluorescent dopant and as a phosphorescenthost when combinedly used with a phosphorescent dopant. Therefore, thefluorescent host and the phosphorescent host are not distinguished fromeach other merely by the difference in their molecular structures.Namely, the term “phosphorescent host” means a material for constitutinga phosphorescent emitting layer containing a phosphorescent dopant anddoes not mean that the material is not usable as a material forconstituting a fluorescent emitting layer. The same also applies to thefluorescent host.

Substrate

In an preferred embodiment, the organic EL device of the invention isformed on a light-transmissive substrate. The light-transmissivesubstrate serves as a support for the organic EL device and preferably aflat substrate having a transmittance of 50% or more to 400 to 700 nmvisible light. Examples of the substrate include a glass plate and apolymer plate. The glass plate may include a plate made of soda-limeglass, barium-strontium-containing glass, lead glass, aluminosilicateglass, borosilicate glass, barium borosilicate glass, or quartz. Thepolymer plate may include a plate made of polycarbonate, acryl,polyethylene terephthalate, polyether sulfide, or polysulfone.

Anode

The anode of the organic EL device injects holes to the holetransporting layer or the light emitting layer, and an anode having awork function of 4.5 eV or more is effective. Examples of material foranode include indium tin oxide alloy (ITO), tin oxide (NESA), indiumzinc oxide alloy, gold, silver, platinum, and cupper. The anode isformed by making the electrode material into a thin film by a method,such as a vapor deposition method or a sputtering method. When gettingthe light emitted from the light emitting layer through the anode, thetransmittance of anode to visible light is preferably 10% or more. Thesheet resistance of anode is preferably several hundreds Ω/□ or less.The film thickness of anode depends upon the kind of material andgenerally 10 nm to 1 μm, preferably 10 to 200 nm.

Cathode

The cathode injects electrons to the electron injecting layer, theelectron transporting layer or the light emitting layer, and preferablyformed from a material having a small work function. Examples of thematerial for cathode include, but not limited to, indium, aluminum,magnesium, magnesium-indium alloy, magnesium-aluminum alloy,aluminum-lithium alloy, aluminum-scandium-lithium alloy, andmagnesium-silver alloy. Like the anode, the cathode is formed by makingthe material into a thin film by a method, such as the vapor depositionmethod and the sputtering method. The emitted light may be taken fromthe cathode, if appropriate.

Light Emitting Layer

The light emitting layer is an organic layer having a light emittingfunction and contains a host material and a dopant material when adoping system is employed. The major function of the host material is topromote the recombination of electrons and holes and confine excitons inthe light emitting layer. The dopant material causes the excitonsgenerated by recombination to emit light efficiently.

In case of a phosphorescent device, the major function of the hostmaterial is to confine the excitons generated on the dopant in the lightemitting layer.

To control the carrier balance in the light emitting layer, the lightemitting layer may be made into a double host (host/co-host) layer, forexample, by combinedly using an electron transporting host and a holetransporting host. In a preferred embodiment, the light emitting layercomprises a first host material and a second host material, wherein thefirst host material is the material for organic EL device of theinvention.

The light emitting layer may be made into a double dopant layer, inwhich two or more kinds of dopant materials having high quantum yieldare combinedly used and each dopant material emits light with its owncolor. For example, to obtain a yellow emission, a light emitting layerformed by co-depositing a host, a red-emitting dopant and agreen-emitting dopant is used.

In a laminate of two or more light emitting layers, electrons and holesare accumulated in the interface between the light emitting layers, andtherefore, the recombination region is localized in the interfacebetween the light emitting layers, to improve the quantum efficiency.

The light emitting layer may be different in the hole injection abilityand the electron injection ability, and also in the hole transportingability and the electron transporting ability each being expressed bymobility.

The light emitting layer is formed, for example, by a known method, suchas a vapor deposition method, a spin coating method, and LB method(Langmuir Blodgett method). Alternatively, the light emitting layer maybe formed by making a solution of a binder, such as resin, and thematerial for the light emitting layer in a solvent into a thin film by amethod such as spin coating.

The light emitting layer is preferably a molecular deposit film. Themolecular deposit film is a thin film formed by depositing a vaporizedmaterial or a film formed by solidifying a material in the state ofsolution or liquid. The molecular deposit film can be distinguished froma thin film formed by LB method (molecular build-up film) by thedifferences in the assembly structures and higher order structures andthe functional difference due to the structural differences.

The dopant material is selected from known fluorescent dopants andphosphorescent dopants.

Examples of the fluorescent dopant include fluoranthene derivative,pyrene derivative, arylacetylene derivative, fluorene derivative, boroncomplex, perylene derivative, oxadiazole derivative, anthracenederivative, and chrysene derivative, with fluoranthene derivative,pyrene derivative, and boron complex being preferred.

The phosphorescent dopant (phosphorescent emitting material) is acompound which emits light by releasing the energy of excited tripletstate and preferably a organometallic complex comprising at least onemetal selected from Ir, Pt, Os, Au, Cu, Re, and Ru and a ligand,although not particularly limited thereto as long as emitting light byreleasing the energy of excited triplet state. A ligand having an orthometal bond is preferred. In view of obtaining a high phosphorescentquantum yield and further improving the external quantum efficiency ofelectroluminescence device, a metal complex comprising a metal selectedfrom Ir, Os, and Pt is preferred, with iridium complex, osmium complex,and platinum, particularly an ortho metallated complex thereof beingmore preferred, iridium complex and platinum complex being still morepreferred, and an ortho metallated iridium complex being particularlypreferred.

The content of the phosphorescent dopant in the light emitting layer isnot particularly limited and selected according to the use of thedevice, and preferably 0.1 to 70% by mass, and more preferably 1 to 30%by mass. If being 0.1% by mass or more, the amount of light emission issufficient. If being 70% by mass or less, the concentration quenchingcan be avoided.

Preferred examples of the organometallic complex usable as thephosphorescent dopant are shown below.

The phosphorescent host is a compound which confines the triplet energyof the phosphorescent dopant efficiently in the light emitting layer tocause the phosphorescent dopant to emit light efficiently. The materialfor organic EL device of the invention is suitable as the phosphorescenthost. The material for organic EL device of the invention may be used inthe light emitting layer singly or in combination of two or more.

When the material for organic EL device of the invention is used in thelight emitting layer as a host material, the emission wavelength of thephosphorescent dopant used is not particularly limited. In a preferredembodiment, at least one of the phosphorescent dopants used in the lightemitting layer has the peak of emission wavelength of preferably 490 nmor longer and 700 nm or shorter and more preferably 490 nm or longer and650 nm or shorter. The emission color of the light emitting layer ispreferably red, yellow and green. An organic EL device with a longlifetime can be obtained by a light emitting layer comprising thecompound of the invention as the host material which is doped with aphosphorescent dopant material emitting light with a wavelength withinthe above ranges.

In an embodiment of the organic EL device of the invention, a compoundother than the material for organic EL device of the invention may besuitably selected as the phosphorescent host material according to theuse of the device.

The material for organic EL device of the invention and a compound otherthan that may be combinedly used in the same light emitting layer as thephosphorescent host material. If two or more light emitting layers areformed, the material for organic EL device of the invention can be usedin one light emitting layer as the phosphorescent host material and acompound other than the material for organic EL device of the inventioncan be used in another light emitting layer as the phosphorescent hostmaterial. The material for organic EL device of the invention may beused in an organic layer other than the light emitting layer. If used inan organic layer other than the light emitting layer, a compound otherthan the material for organic EL device of the invention can be used inthe light emitting layer as the phosphorescent host material.

Examples of the compounds other than the material for organic EL deviceof the invention, which are suitable as the phosphorescent host, includea carbazole derivative, a triazole derivative, a oxazole derivative, anoxadiazole derivative, an imidazole derivative, a polyarylalkanederivative, a pyrazoline derivative, a pyrazolone derivative, aphenylenediamine derivative, an arylamine derivative, anamino-substituted chalcone derivative, a styrylanthracene derivative, afluorenone derivative, a hydrazone derivative, a stilbene derivative, asilazane derivative, an aromatic tertiary amine compound, a styrylaminecompound, an aromatic methylidene compound, a porphyrin compound, ananthraquinodimethane derivative, an anthrone derivative, adiphenylquinone derivative, a thiopyran dioxide derivative, acarbodiimide derivative, a fluorenylidenemethane derivative, adistyrylpyrazine derivative, a tetracarboxylic anhydride of fused ringsuch as naphthalene and perylene, a phthalocyanine derivative, a metalcomplex of 8-quinolinol derivative, metal phthalocyanine, metalcomplexes having a ligand such as benzoxazole and benzothiazole, anelectroconductive oligomer, such as a polysilane compound, apoly(N-vinylcarbazole) derivative, an aniline copolymer, thiopheneoligomer, and a polythiophene, and a polymer such as a polythiophenederivative, a polyphenylene derivative, a polyphenylenevinylenederivative, and a polyfluorene derivative. These phosphorescent hostsmay be used alone or in combination of two or more. Specific examplesthereof are shown below.

In an embodiment of the invention, the light emitting layer may comprisea first host material and a second host material, wherein the first hostmaterial is the material for organic EL device of the invention and thesecond host material is a compound other than the material for organicEL device of the invention. In the present invention, the terms “firsthost material” and “second host material” are used merely forstructurally distinguishing the two or more host materials in the lightemitting layer and are not determined according to the content of eachhost material in the light emitting layer.

The second host material is not particularly limited and may be selectedfrom the compounds mentioned above with respect to the suitablephosphorescent host other than the material for organic EL device of theinvention. The second host material is preferably selected from thecompounds represented by the following formulae (1) to (4), because thelifetime of organic EL device is prolonged. Also preferred as the secondhost material is a compound having no cyano group. A carbazolederivative, an arylamine derivative, a fluorenone derivative, and anaromatic tertiary amine are also preferred as the second host material.

wherein

Z¹¹ represents a ring structure fused to the side a and represented byformula (1-1) or (1-2), and Z¹² represents a ring structure fused to theside b and represented by formula (1-1) or (1-2), provided that at leastone of Z¹¹ and Z¹² is represented by formula (1-1);

M¹ represent a substituted or unsubstituted nitrogen-containing aromaticheteroring having 5 to 30 ring atoms;

L¹ represents a single bond, a substituted or unsubstituted divalentaromatic hydrocarbon group having 6 to 30 ring carbon atoms, asubstituted or unsubstituted divalent heterocyclic group having 5 to 30ring atoms, a cycloalkylene group having 5 to 30 ring atoms, or a groupin which the preceding groups are directly linked to each other; and

k represents 1 or 2.

In formula (1-1), a side c is fused to the side a or b of formula (1).

In formula (1-2), any one of sides d, e and f is fused to the side a orb of formula (1).

In formulae (1-1) and (1-2),

X¹¹ represents a sulfur atom, an oxygen atom, N—R¹⁹, or C(R²⁰)(R²¹); and

each of R¹¹ to R²¹ independently represents a hydrogen atom, a heavyhydrogen atom, a halogen atom, a cyano group, a substituted orunsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms, a substituted or unsubstituted heterocyclic group having 5 to 30ring atoms, a substituted or unsubstituted alkyl group having 1 to 30carbon atoms, a substituted or unsubstituted alkenyl group having 2 to30 carbon atoms, a substituted or unsubstituted alkynyl group having 2to 30 carbon atoms, a substituted or unsubstituted alkylsilyl grouphaving 3 to 30 carbon atoms, a substituted or unsubstituted arylsilylgroup having 6 to 30 ring carbon atoms, a substituted or unsubstitutedalkoxy group having 1 to 30 carbon atoms, a substituted or unsubstitutedaralkyl group having 6 to 30 ring carbon atoms, or a substituted orunsubstituted aryloxy group having 6 to 30 ring carbon atoms, providedthat adjacent groups of R¹¹ to R²¹ may be bonded to each other to form aring.

The nitrogen-containing aromatic heteroring represented by M¹ of formula(1) may include an azine rings.

Examples of the nitrogen-containing aromatic heteroring includepyridine, pyrimidine, pyrazine, triazine, aziridine, azaindolizine,indolizine, imidazole, indole, isoindole, indazole, purine, pteridine,β-carboline, naphthyridine, quinoxaline, terpyridine, bipyridine,acridine, phenanthroline, phenazine, and imidazopyridine, with pyridine,pyrimidine, and triazine being particularly preferred. The formula (1)is preferably represented by formula (2):

wherein

Z¹¹ represents a ring structure fused to the side a and represented byformula (1-1) or (1-2), and Z¹² represents a ring structure fused to theside b and represented by formula (1-1) or (1-2), provided that at leastone of Z¹¹ and Z¹² is represented by formula (1-1);

L² is as defined in formula (1);

each of X¹² to X¹⁴ independently represents a nitrogen atom, CH, or acarbon atom bonded to R³¹ or L², provided that at least one of X¹² toX¹⁴ represents a nitrogen atom;

each of Y¹¹ to Y¹³ independently represents CH or a carbon atom bondedto R³¹ or L²;

each of R³¹ independently represents a halogen atom, a cyano group, asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 30ring carbon atoms, a substituted or unsubstituted heterocyclic grouphaving 5 to 30 ring atoms, a substituted or unsubstituted alkyl grouphaving 1 to 30 carbon atoms, a substituted or unsubstituted alkenylgroup having 2 to 30 carbon atoms, a substituted or unsubstitutedalkynyl group having 2 to 30 carbon atoms, a substituted orunsubstituted alkylsilyl group having 3 to 30 carbon atoms, asubstituted or unsubstituted arylsilyl group having 6 to 30 ring carbonatoms, a substituted or unsubstituted alkoxy group having 1 to 30 carbonatoms, a substituted or unsubstituted aralkyl group having 6 to 30 ringcarbon atoms, or a substituted or unsubstituted aryloxy group having 6to 30 ring carbon atoms;

when two or more R³¹ groups exist, the R³¹ groups may be the same ordifferent and adjacent R³¹ groups may be bonded to each other to form aring;

k represents 1 or 2, and m represents an integer of 0 to 4;

the side c of formula (1-1) is fused to the side a or b of formula (2);and

any one of sides d, e and f of formula (1-2) is fused to the side a or bof formula (2).

Examples of the compound wherein the ring represented by formula (1-1)or (1-2) is fused to the side a or b of formula (2) are shown below.

The compound represented by formula (1) or (2) is more preferablyrepresented by formula (3) and particularly preferably represented byformula (4).

In formula (3),

L² is as defined in formula (1);

each of X¹² to X¹⁴ independently represents a nitrogen atom, CH, or acarbon atom bonded to R³¹ or L², provided that at least one of X¹² toX¹⁴ represents a nitrogen atom;

each of Y¹¹ to Y¹³ independently represents CH or a carbon atom bondedto R³¹ or L²;

each of R³¹ independently represents a halogen atom, a cyano group, asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 30ring carbon atoms, a substituted or unsubstituted heterocyclic grouphaving 5 to 30 ring atoms, a substituted or unsubstituted alkyl grouphaving 1 to 30 carbon atoms, a substituted or unsubstituted alkenylgroup having 2 to 30 carbon atoms, a substituted or unsubstitutedalkynyl group having 2 to 30 carbon atoms, a substituted orunsubstituted alkylsilyl group having 3 to 30 carbon atoms, asubstituted or unsubstituted arylsilyl group having 6 to 30 ring carbonatoms, a substituted or unsubstituted alkoxy group having 1 to 30 carbonatoms, a substituted or unsubstituted aralkyl group having 6 to 30 ringcarbon atoms, or a substituted or unsubstituted aryloxy group having 6to 30 ring carbon atoms;

when two or more R³¹ groups exist, the R³¹ groups may be the same ordifferent and adjacent R³¹ groups may be bonded to each other to form aring;

m represents an integer of 0 to 4;

each of R⁴¹ to R⁴⁸ independently represents a hydrogen atom, a heavyhydrogen atom, a halogen atom, a cyano group, a substituted orunsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms, a substituted or unsubstituted heterocyclic group having 5 to 30ring atoms, a substituted or unsubstituted alkyl group having 1 to 30carbon atoms, a substituted or unsubstituted alkenyl group having 2 to30 carbon atoms, a substituted or unsubstituted alkynyl group having 2to 30 carbon atoms, a substituted or unsubstituted alkylsilyl grouphaving 3 to 30 carbon atoms, a substituted or unsubstituted arylsilylgroup having 6 to 30 ring carbon atoms, a substituted or unsubstitutedalkoxy group having 1 to 30 carbon atoms, a substituted or unsubstitutedaralkyl group having 6 to 30 ring carbon atoms, or a substituted orunsubstituted aryloxy group having 6 to 30 ring carbon atoms; and

adjacent groups of R⁴¹ to R⁴⁸ may be bonded to each other to form aring.

In formula (4),

L² is as defined in formula (1);

each of X¹² to X¹⁴ independently represents a nitrogen atom, CH, or acarbon atom bonded to R³¹ or L², provided that at least one of X¹² toX¹⁴ represents a nitrogen atom;

each of Y¹¹ to Y¹³ independently represents CH or a carbon atom bondedto R³¹ or L²;

each of R³¹ independently represents a halogen atom, a cyano group, asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 30ring carbon atoms, a substituted or unsubstituted heterocyclic grouphaving 5 to 30 ring atoms, a substituted or unsubstituted alkyl grouphaving 1 to 30 carbon atoms, a substituted or unsubstituted alkenylgroup having 2 to 30 carbon atoms, a substituted or unsubstitutedalkynyl group having 2 to 30 carbon atoms, a substituted orunsubstituted alkylsilyl group having 3 to 30 carbon atoms, asubstituted or unsubstituted arylsilyl group having 6 to 30 ring carbonatoms, a substituted or unsubstituted alkoxy group having 1 to 30 carbonatoms, a substituted or unsubstituted aralkyl group having 6 to 30 ringcarbon atoms, or a substituted or unsubstituted aryloxy group having 6to 30 ring carbon atoms;

adjacent R³¹ groups may be bonded to each other to form a ring;

m represents an integer of 0 to 4;

each of L³ and L⁴ independently represents a single bond, a substitutedor unsubstituted divalent aromatic hydrocarbon group having 6 to 30 ringcarbon atoms, a substituted or unsubstituted divalent heterocyclic grouphaving 5 to 30 ring atoms, a cycloalkylene group having 5 to 30 ringatoms, or a group in which the preceding groups are directly linked toeach other;

each of R⁵¹ to R⁵⁴ independently represents a halogen atom, a cyanogroup, a substituted or unsubstituted aromatic hydrocarbon group having6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclicgroup having 5 to 30 ring atoms, a substituted or unsubstituted alkylgroup having 1 to 30 carbon atoms, a substituted or unsubstitutedalkenyl group having 2 to 30 carbon atoms, a substituted orunsubstituted alkynyl group having 2 to 30 carbon atoms, a substitutedor unsubstituted alkylsilyl group having 3 to 30 carbon atoms, asubstituted or unsubstituted arylsilyl group having 6 to 30 ring carbonatoms, a substituted or unsubstituted alkoxy group having 1 to 30 carbonatoms, a substituted or unsubstituted aralkyl group having 6 to 30 ringcarbon atoms, or a substituted or unsubstituted aryloxy group having 6to 30 ring carbon atoms;

when two or more R⁵¹ groups exist, the R⁵¹ groups may be the same ordifferent and adjacent R⁵¹ groups may be bonded to each other to form aring;

when two or more R⁵² groups exist, the R⁵² groups may be the same ordifferent and adjacent R⁵² groups may be bonded to each other to form aring;

when two or more R⁵³ groups exist, the R⁵³ groups may be the same ordifferent and adjacent R⁵³ groups may be bonded to each other to form aring;

when two or more R⁵⁴ groups exist, the R⁵⁴ groups may be the same ordifferent and adjacent R⁵⁴ groups may be bonded to each other to form aring;

M² represents a substituted or unsubstituted aromatic hydrocarbon grouphaving 6 to 30 ring carbon atoms or a substituted or unsubstitutedheterocyclic group having 5 to 30 ring atoms; and

each of p and s independently represents an integer of 0 to 4, and eachof q and r independently represents an integer of 0 to 3.

In formulae (1) to (4), (1-1), and (1-2), the groups represented by R¹¹to R²¹, R³¹, R⁴¹ to R⁴⁸, and R⁵¹ to R⁵⁴ are as defined above withrespect to formula (I).

Examples of the divalent aromatic hydrocarbon group having 6 to 30 ringcarbon atoms and the divalent heterocyclic group having 5 to 30 ringatoms represented by L² to L⁴ of formulae (1) to (4) includes divalentresidues of the corresponding aromatic hydrocarbon groups andheterocyclic groups described above with respect to formula (I).

Examples of the compounds represented by any of formulae (1) to (4) areshown below. In the following structural formulae, the bond notterminated with a chemical symbol or structure (for example, CN andbenzene ring) denotes a methyl group.

In an embodiment of the organic EL device of the invention, thethickness of the light emitting layer is preferably 5 to 50 nm, morepreferably 7 to 50 nm, and still more preferably 10 to 50 nm. If being 5nm or more, the light emitting layer is easily formed. If being 50 nm orless, the increase in driving voltage is avoided.

Electron-Donating Dopant

In a preferred embodiment of the invention, the organic EL device maycontain an electron-donating dopant in the interfacial region betweenthe cathode and the light emitting unit. With such a construction, theorganic EL device has an improved luminance and an elongated lifetime.The electron-donating dopant is a metal having a work function of 3.8 eVor less or a compound containing such metal. Examples thereof include atleast one compound selected from alkali metal, alkali metal complex,alkali metal compound, alkaline earth metal, alkaline earth metalcomplex, alkaline earth metal compound, rare earth metal, rare earthmetal complex, and rare earth metal compound.

Examples of the alkali metal include Na (work function: 2.36 eV), K(work function: 2.28 eV), Rb (work function: 2.16 eV), and Cs (workfunction: 1.95 eV), with those having a work function of 2.9 eV or lessbeing particularly preferred. Of the above, preferred are K, Rb, and Cs,more preferred are Rb and Cs, and most preferred is Cs. Examples of thealkaline earth metal include Ca (work function: 2.9 eV), Sr (workfunction: 2.0 to 2.5 eV), and Ba (work function: 2.52 eV), with thosehaving a work function of 2.9 eV or less being particularly preferred.Examples of the rare earth metal include Sc, Y, Ce, Tb, and Yb, withthose having a work function of 2.9 eV or less being particularlypreferred.

Examples of the alkali metal compound include alkali oxide, such asLi₂O, Cs₂O, K₂O, and alkali halide, such as LiF, NaF, CsF, and KF, withLiF, Li₂O, and NaF being preferred. Examples of the alkaline earth metalcompound include BaO, SrO, CaO, and mixture thereof, such asBa_(x)Sr_(1-x)O (0<x<1) and Ba_(x)CA¹ _(−x)O (0<x<1), with BaO, SrO, andCaO being preferred. Examples of the rare earth metal compound includeYbF₃, ScF₃, ScO₃, Y₂O₃, Ce₂O₃, GdF₃, and TbF₃, with YbF₃, ScF₃, and TbF₃being preferred.

Examples of the alkali metal complex, alkaline earth metal complex, andrare earth metal are not particularly limited as long as containing atleast one metal ion selected from alkali metal ions, alkaline earthmetal ions, rare earth metal ions, respectively. The ligand ispreferably, but not limited to, quinolinol, benzoquinolinol, acridinol,phenanthridinol, hydroxyphenyloxazole, hydroxyphenylthiazole,hydroxydiaryloxadiazole, hydroxydiarylthiadiazole,hydroxyphenylpyridine, hydroxyphenylbenzimidazole, hydroxybenzotriazole,hydroxyfulborane, bipyridyl, phenanthroline, phthalocyanine, porphyrin,cyclopentadiene, β-diketones, azomethines, and derivative thereof.

The electron-donating dopant is added to the interfacial regionpreferably into a form of layer or island. The electron-donating dopantis added preferably by co-depositing the electron-donating dopant withthe organic compound (light emitting material, electron injectingmaterial, etc.) for forming the interfacial region by a resistanceheating deposition method, thereby dispersing the electron-donatingdopant into the organic material. The disperse concentration expressedby the molar ratio of the organic material and the electron-donatingdopant is 100:1 to 1:100 and preferably 5:1 to 1:5.

When the electron-donating dopant is formed into a form of layer, alight emitting material or an electron injecting material is made into alayer which serves as an organic layer in the interface, and then, theelectron-donating dopant alone is deposited by a resistance heatingdeposition method into a layer having a thickness preferably 0.1 to 15nm. When the electron-donating dopant is formed into a form of island, alight emitting material or an electron injecting material is made into aform of island which serves as an organic layer in the interface, andthen, the electron-donating dopant alone is deposited by a resistanceheating deposition method into a form of island having a thicknesspreferably 0.05 to 1 nm.

The molar ratio of the main component and the electron-donating dopantin the organic electroluminescence device of the invention is preferably5:1 to 1:5 and more preferably 2:1 to 1:2.

Electron Transporting Layer

The electron transporting layer is an organic layer disposed between thelight emitting layer and the cathode and transports electrons from thecathode to the light emitting layer. If two or more electrontransporting layers are provided, the organic layer closer to thecathode may be called an electron injecting layer in some cases. Theelectron injecting layer injects electrons from the cathode to theorganic layer unit efficiently.

An aromatic heterocyclic compound having one or more heteroatoms in itsmolecule is preferably used as the electron transporting material forthe electron transporting layer, with a nitrogen-containing ringderivative being particularly preferred. The nitrogen-containing ringderivative is preferably an aromatic ring compound having anitrogen-containing 6- or 5-membered ring or a condensed aromatic ringcompound having a nitrogen-containing 6- or 5-membered ring.

The nitrogen-containing ring derivative is preferably, for example, achelate metal complex having a nitrogen-containing ring represented byformula (A).

R² to R⁷ of formula (A) each independently represent a hydrogen atom, ahalogen atom, a hydroxyl group, an amino group, a hydrocarbon grouphaving 1 to 40 carbon atoms, an alkoxy group having 1 to 40 carbonatoms, an aryloxy group having 6 to 50 carbon atoms, an alkoxycarbonylgroup, or a heterocyclic group having 5 to 50 carbon atoms, each beingoptionally substituted.

The halogen atom may include fluorine, chlorine, bromine, and iodine.

The substituted amino group may include an alkylamino group, anarylamino group, and an aralkylamino group.

The alkylamino group and the aralkylamino group are represented by—NQ¹Q², wherein Q¹ and Q² each independently represent an alkyl grouphaving 1 to 20 carbon atoms or an aralkyl group having 1 to 20 carbonatoms. One of Q¹ and Q² may be a hydrogen atom.

The arylamino group is represented by —NAr¹Ar², wherein Ar¹ and Ar² eachindependently represent a non-condensed aromatic hydrocarbon group or acondensed aromatic hydrocarbon group each having 6 to 50 carbon atoms.One of Ar¹ and Ar² may be a hydrogen atom.

The hydrocarbon group having 1 to 40 carbon atoms may include an alkylgroup, an alkenyl group, a cycloalkyl group, an aryl group, and anaralkyl group.

The alkoxycarbonyl group is represented by —COOY′, wherein Y′ is analkyl group having 1 to 20 carbon atoms.

M is aluminum (Al), gallium (Ga), or indium (In), with In beingpreferred.

L is a group represented by formula (A′) or (A″):

R⁸ to R¹² in formula (A′) each independently represent a hydrogen atomor a substituted or unsubstituted hydrocarbon group having 1 to 40carbon atoms. The adjacent two groups may form a ring structure. R¹³ toR²⁷ in formula (A″) each independently represent a hydrogen atom or asubstituted or unsubstituted hydrocarbon group having 1 to 40 carbonatoms. The adjacent two groups may form a ring structure.

Examples of the hydrocarbon group having 1 to 40 carbon atoms for R⁸ toR¹² and R¹³ to R²⁷ in formulae (A′) and (A″) are the same as thosedescribed above with respect to R² to R⁷ of formula (A). Examples of thedivalent group formed by the adjacent two groups of R⁸ to R¹² and R¹³ toR²⁷ which completes the ring structure include tetramethylene group,pentamethylene group, hexamethylene group, diphenylmethane-2,2′-diylgroup, diphenylethane-3,3′-diyl group, and diphenylpropane-4,4′-diylgroup.

The electron transporting compound for the electron transporting layeris preferably a metal complex including 8-hydroxyquinoline or itsderivative, an oxadiazole derivative, and a nitrogen-containingheterocyclic derivative.

Examples of the metal complex including 8-hydroxyquinoline or itsderivative include a metal chelate oxinoid including a chelated oxine(generally, 8-quinolinol or 8-hydroxyquinoline), for example,tris(8-quinolinol)aluminum. Examples of the oxadiazole derivative areshown below.

In the above formulae, each of Ar¹⁷, A¹⁸, Ar¹⁹, Ar²¹, Ar²², and Ar²⁵ isa substituted or unsubstituted aromatic hydrocarbon group or asubstituted or unsubstituted condensed aromatic hydrocarbon group eachhaving 6 to 50 carbon atoms, and Ar¹⁷ and Ar¹⁸, Ar¹⁹ and Ar²¹, and Ar²²and Ar²⁵ may be the same or different. Examples of the aromatichydrocarbon group and the condensed aromatic hydrocarbon group includephenyl group, naphthyl group, biphenyl group, anthranyl group, perylenylgroup, and pyrenyl group. The optional substituent may be an alkyl grouphaving 1 to 10 carbon atoms, an alkoxyl group having 1 to 10 carbonatoms or a cyano group.

Each of Ar²⁰, Ar²³, and Ar²⁴ is a substituted or unsubstituted bivalentaromatic hydrocarbon group or a substituted or unsubstituted bivalentcondensed aromatic hydrocarbon group each having 6 to 50 carbon atoms,and Ar²³ and Ar²⁴ may be the same or different. Examples of the bivalentaromatic hydrocarbon group or the bivalent condensed aromatichydrocarbon group include phenylene group, naphthylene group,biphenylene group, anthranylene group, perylenylene group, andpyrenylene group. The optional substituent may be an alkyl group having1 to 10 carbon atoms, an alkoxyl group having 1 to 10 carbon atoms or acyano group.

Electron transporting compounds which have a good thin film-formingproperty are preferably used. Examples of the electron transportingcompound are shown below.

Examples of the nitrogen-containing heterocyclic derivative for use asthe electron transporting compound include a nitrogen-containingheterocyclic derivative having the following formulae but exclusive ofmetal complex, for example, a compound having a 5- or 6-membered ringwhich has the skeleton represented by formula (B) or having thestructure represented by formula (C).

In formula (C), X is a carbon atom or a nitrogen atom. Z¹ and Z² eachindependently represent a group of atoms for completing thenitrogen-containing heteroring.

The nitrogen-containing heterocyclic derivative is more preferably anorganic compound which has a nitrogen-containing aromatic polycyclicring comprising a 5-membered ring or a 6-membered ring. If two or morenitrogen atoms are included, the nitrogen-containing aromatic polycycliccompound preferably has a skeleton of a combination of (B) and (C) or acombination of (B) and (D).

The nitrogen-containing group of the nitrogen-containing aromaticpolycyclic compound is selected, for example, from thenitrogen-containing heterocyclic groups shown below.

In the above formulae, R is an aromatic hydrocarbon group or a condensedaromatic hydrocarbon group each having 6 to 40 carbon atoms, an aromaticheterocyclic group or a condensed aromatic heterocyclic group eachhaving 3 to 40 carbon atoms, an alkyl group having 1 to 20 carbon atoms,or an alkoxy group having 1 to 20 carbon atoms; and n is an integer of 0to 5. If n is an integer of 2 or more, R groups may be the same ordifferent.

More preferred is a nitrogen-containing heterocyclic derivativerepresented by the following formula:HAr-L¹-Ar¹—Ar²  (D1)wherein HAr is a substitute or unsubstituted nitrogen-containingheterocyclic group having 3 to 40 carbon atoms; L¹ is a single bond, asubstituted or unsubstituted aromatic hydrocarbon group or condensedaromatic hydrocarbon group each having 6 to 40 carbon atoms, or asubstituted or unsubstituted aromatic heterocyclic group or condensedaromatic heterocyclic group each having 3 to 40 carbon atoms; Ar¹ is asubstitute or unsubstituted divalent aromatic hydrocarbon group having 6to 40 carbon atoms; and Ar² is a substitute or unsubstituted aromatichydrocarbon group or condensed aromatic hydrocarbon group each having 6to 40 carbon atoms or a substituted or unsubstituted aromaticheterocyclic group or condensed aromatic heterocyclic group each having3 to 40 carbon atoms.

HAr is selected, for example, from the following groups:

L¹ of formula (D1) is selected, for example, from the following groups:

Ar¹ of formula (D1) is selected, for example, from the followingarylanthranyl groups represented by formula (D2) or (D3):

In the above formulae (D2) and (D3), R¹ to R¹⁴ are each independently ahydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbonatoms, an alkoxy group having 1 to 20 carbon atoms, an aryloxy grouphaving 6 to 40 carbon atoms, a substituted or unsubstituted aromatichydrocarbon group or condensed aromatic hydrocarbon group each having 6to 40 carbon atoms, or a substituted or unsubstituted aromaticheterocyclic group or condensed aromatic heterocyclic group each having3 to 40 carbon atoms; and Ara is a substituted or unsubstituted aromatichydrocarbon group or condensed aromatic hydrocarbon group each having 6to 40 carbon atoms or a substituted or unsubstituted aromaticheterocyclic group or condensed aromatic heterocyclic group each having3 to 40 carbon atoms. R¹ to R⁸ may be all hydrogen atoms.

Ar² of formula (D1) is selected, for example, from the following groups:

In addition, the following compound is preferably used as thenitrogen-containing aromatic polycyclic compound for use as the electrontransporting compound.

In the formula (D4), R¹ to R⁴ each independently represent a hydrogenatom, a substituted or unsubstituted aliphatic group having 1 to 20carbon atoms, a substituted or unsubstituted alicyclic group having 3 to20 carbon atoms, a substituted or unsubstituted aromatic group having 6to 50 carbon atoms, or a substituted or unsubstituted heterocyclic grouphaving 3 to 50 carbon atoms; and X₁ and X₂ each independently representan oxygen atom, a sulfur atom, or dicyanomethylene group.

Further, the following compound is also suitable as the electrontransporting compound.

In the formula (D5), R¹, R², R³, and R⁴ may be the same or different andeach represents an aromatic hydrocarbon group or a condensed aromatichydrocarbon group each represented by the following formula (D6):

In the formula (D6), R⁵, R⁶, R⁷, R⁸, and R⁹ may be the same or differentand each represents a hydrogen atom, a saturated or unsaturated alkoxylgroup having 1 to 20 carbon atoms, a saturated or unsaturated alkylgroup having 1 to 20 carbon atoms, an amino group, or an alkylaminogroup having 1 to 20 carbon atoms. At least one of R⁵, R⁶, R⁷, R⁸, andR⁹ is a group other than hydrogen atom.

Further, a polymer having the nitrogen-containing heterocyclic group orthe nitrogen-containing heterocyclic derivative is also usable as theelectron transporting compound.

In an embodiment of the organic EL device of the invention, it isparticularly preferred for the electron transporting layer to contain atleast one of the nitrogen-containing heterocyclic derivativesrepresented by the following formulae (E) to (G).

In the formulae (E) to (G), Z¹, Z², and Z³ each independently representa nitrogen atom or a carbon atom.

R¹ and R² each independently represent a substituted or unsubstitutedaryl group having 6 to 50 ring carbon atoms, a substituted orunsubstituted heteroaryl group having 5 to 50 ring atoms, a substitutedor unsubstituted alkyl group having 1 to 20 carbon atoms, a substitutedor unsubstituted haloalkyl group having 1 to 20 carbon atoms, or asubstituted or unsubstituted alkoxyl group having 1 to 20 carbon atoms.

The subscript n is an integer of 0 to 5. If n is an integer of 2 ormore, R¹ groups may be the same or different from each other. Theadjacent two R¹ groups may bond to each other to form a substituted orunsubstituted hydrocarbon ring.

Ar¹ represents a substituted or unsubstituted aryl group having 6 to 50ring carbon atoms or a substituted or unsubstituted heteroaryl grouphaving 5 to 50 ring atoms.

Ar² represents a hydrogen atom, a substituted or unsubstituted alkylgroup having 1 to 20 carbon atoms, a substituted or unsubstitutedhaloalkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted alkoxyl group having 1 to 20 carbon atoms, a substitutedor unsubstituted aryl group having 6 to 50 ring carbon atoms, or asubstituted or unsubstituted heteroaryl group having 5 to 50 ring atoms.

However, one of Ar¹ and Ar² is a substituted or unsubstituted condensedaromatic hydrocarbon group having 10 to 50 ring carbon atoms or asubstituted or unsubstituted condensed aromatic heterocyclic grouphaving 9 to 50 ring atoms.

Ar³ represents a substituted or unsubstituted arylene group having 6 to50 ring carbon atoms or a substituted or unsubstituted heteroarylenegroup having 5 to 50 ring atoms.

L¹, L², and L³ each independently represent a single bond, a substitutedor unsubstituted arylene group having 6 to 50 ring carbon atoms or asubstituted or unsubstituted divalent condensed aromatic heterocyclicgroup having 9 to 50 ring atoms.

Examples of the aryl group having 6 to 50 ring carbon atoms includephenyl group, naphthyl group, anthryl group, phenanthryl group,naphthacenyl group, chrysenyl group, pyrenyl group, biphenyl group,terphenyl group, tolyl group, fluoranthenyl group, and fluorenyl group.

Examples of the heteroaryl group having 5 to 50 ring atoms includepyrrolyl group, furyl group, thiophenyl group, silolyl group, pyridylgroup, quinolyl group, isoquinolyl group, benzofuryl group, imidazolylgroup, pyrimidyl group, carbazolyl group, selenophenyl group,oxadiazolyl group, triazolyl group, pyrazinyl group, pyridazinyl group,triazinyl group, quinoxalinyl group, acridinyl group,imidazo[1,2-a]pyridinyl group, and imidazo[1,2-a]pyrimidinyl.

Examples of the alkyl group having 1 to 20 carbon atoms include methylgroup, ethyl group, propyl group, butyl group, pentyl group, and hexylgroup.

Examples of the haloalkyl group having 1 to 20 carbon atoms include thegroups obtained by replacing one or more hydrogen atoms of the alkylgroup mentioned above with at least one halogen atom selected fromfluorine, chlorine, iodine, and bromine.

Examples of the alkyl moiety of the alkoxyl group having 1 to 20 carbonatoms include the alkyl group mentioned above.

Examples of the arylene groups include the groups obtained by removingone hydrogen atom from the aryl group mentioned above.

Examples of the divalent condensed aromatic heterocyclic group having 9to 50 ring atoms include the groups obtained by removing one hydrogenatom from the condensed aromatic heterocyclic group mentioned above asthe heteroaryl group.

The thickness of the electron transporting layer is preferably 1 to 100nm, although not particularly limited thereto.

The electron injecting layer which may be formed adjacent to theelectron transporting layer preferably includes an inorganic compound,such as an insulating material and a semiconductor in addition to thenitrogen-containing ring derivative. The insulating material orsemiconductor incorporated into the electron injecting layer effectivelyprevents the leak of electric current to enhance the electron injectingproperties.

The insulating material is preferably at least one metal compoundselected from the group consisting of alkali metal chalcogenides,alkaline earth metal chalcogenides, alkali metal halides and alkalineearth metal halides. The alkali metal chalcogenide, etc. incorporatedinto the electron injecting layer further enhances the electroninjecting properties. Preferred examples of the alkali metalchalcogenides include Li₂O, K₂O, Na₂S, Na₂Se and Na₂O, and preferredexamples of the alkaline earth metal chalcogenides include CaO, BaO,SrO, BeO, BaS and CaSe. Preferred examples of the alkali metal halidesinclude LiF, NaF, KF, LiCl, KCl and NaCl. Examples of the alkaline earthmetal halides include fluorides such as CaF², BaF², SrF₂, MgF² and BeF²and halides other than fluorides.

Examples of the semiconductor may include oxide, nitride or oxynitrideeach containing at least one element selected from the group consistingof Ba, Ca, Sr, Yb, Al, Ga, In, Li, Na, Cd, Mg, Si, Ta, Sb and Zn. Thesemiconductor may be used singly or in combination of two or more. Theinorganic compound forming the electron injecting layer preferably formsa microcrystalline or amorphous insulating thin film. When the electroninjecting layer is formed from such an insulating thin film, the thinfilm is made more uniform to decrease the pixel defects such as darkspots. Examples of such inorganic compound include alkali metalchalcogenides, alkaline earth metal chalcogenides, alkali metal halidesand alkaline earth metal halide, each being described above.

The thickness of the layer including the insulating material or thesemiconductor is preferably about 0.1 to 15 nm. The electron injectinglayer may be included with the electron-donating dopant described above.

Hole Transporting Layer

The hole transporting layer is an organic layer formed between the lightemitting layer and the anode and has a function of transporting holesfrom the anode to the light emitting layer. When the hole transportinglayer is formed by two or more layers, the layer closer to the anode maybe defined as the hole injecting layer in some cases. The hole injectinglayer has a function of efficiently injecting holes from the anode tothe organic layer unit.

An aromatic amine compound, for example, the aromatic amine derivativerepresented by formula (H), is also preferably used as the material forforming the hole transporting layer.

In the formula (H), each of Ar¹ to Ar⁴ represents a substituted orunsubstituted aromatic hydrocarbon group or condensed aromatichydrocarbon group having 6 to 50 ring carbon atoms, a substituted orunsubstituted aromatic heterocyclic group or condensed aromaticheterocyclic group having 5 to 50 ring atoms, or a group wherein thearomatic hydrocarbon group or condensed aromatic hydrocarbon group andthe aromatic heterocyclic group or condensed aromatic heterocyclic groupare boned to each other.

L represents a substituted or unsubstituted aromatic hydrocarbon groupor condensed aromatic hydrocarbon group each having 6 to 50 ring carbonatoms or a substituted or unsubstituted aromatic heterocyclic group orcondensed aromatic heterocyclic group each having 5 to 50 ring atoms.

Specific examples of the compound represented by the formula (H) areshown below.

The aromatic amine represented by the formula (J) is also preferablyused as the material for forming the hole transporting layer.

In the formula (J), each of Ar¹ to Ar³ is defined in the same manner asin the definition of Ar¹ to Ar⁴ of the formula (H). The specificexamples of the compounds represented by the formula (J) are shownbelow, although not limited thereto.

In an embodiment of the organic EL device of the invention, the holetransporting layer may be made into two-layered structure of a firsthole transporting layer (anode side) and a second hole transportinglayer (cathode side).

The thickness of the hole transporting layer is preferably 10 to 200 nm,although not particularly limited thereto.

In an embodiment of the organic EL device of the invention, the organicEL device may have a layer comprising an acceptor material which isattached to the anode side of each of the hole transporting layer andthe first hole transporting layer. With such a layer, it is expectedthat the driving voltage is lowered and the production cost is reduced.

The acceptor material is preferably a compound represented by theformula (K):

wherein R₂₁ to R₂₆ may be the same or different and each independentlyrepresent a cyano group, —CONH₂, a carboxyl group, or —COOR₂₇ whereinR₂₇ represents an alkyl group having 1 to 20 carbon atoms or acycloalkyl group having 3 to 20 carbon atoms. One or more of a pair ofR₂₁ and R₂₂, a pair of R₂₃ and R₂₄, and a pair of R₂₅ and R₂₆ may bondto each other to form a group represented by —CO—O—CO—.

Examples of R₂₇ include methyl group, ethyl group, n-propyl group,isopropyl group, n-butyl group, isobutyl group, t-butyl group,cyclopentyl group, and cyclohexyl group.

The thickness of the layer comprising the acceptor material ispreferably 5 to 20 nm, although not particularly limited thereto.

N/P Doping

The carrier injecting properties of the hole transporting layer and theelectron transporting layer can be controlled by, as described in JP3695714B, the doping (n) with a donor material or the doping (p) with anacceptor material.

A typical example of the n-doping is an electron transporting materialdoped with a metal, such as Li and Cs, and a typical example of thep-doping is a hole transporting material doped with an acceptor materialsuch as, F₄TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane).

Space Layer

For example, in an organic EL device wherein a fluorescent lightemitting layer and a phosphorescent light emitting layer are laminated,a space layer is disposed between the fluorescent light emitting layerand the phosphorescent light emitting layer to prevent the diffusion ofexcitons generated in the phosphorescent light emitting layer to thefluorescent light emitting layer or to control the carrier balance. Thespace layer may be disposed between two or more phosphorescent lightemitting layers.

Since the space layer is disposed between the light emitting layers, amaterial combining the electron transporting ability and the holetransporting ability is preferably used for forming the space layer. Toprevent the diffusion of triplet energy in the adjacent phosphorescentlight emitting layer, the triplet energy of the material for the spacelayer is preferably 2.6 eV or more. The materials described with respectto the hole transporting layer are usable as the material for the spacelayer.

Blocking Layer

In an embodiment of the invention, the organic EL device preferably hasa blocking layer, such as an electron blocking layer, a hole blockinglayer, and a triplet blocking layer, which is disposed adjacent to thelight emitting layer. The electron blocking layer is a layer whichprevents the diffusion of electrons from the light emitting layer to thehole transporting layer. The hole blocking layer is a layer whichprevents the diffusion of holes from the light emitting layer to theelectron transporting layer. The material for organic EL device of theinvention is also usable as the material for the hole blocking layer.

The triplet blocking layer prevents the diffusion of triplet excitonsgenerated in the light emitting layer to adjacent layers and has afunction of confining the triplet excitons in the light emitting layer,thereby preventing the deactivation of energy on molecules other thanthe emitting dopant of triplet excitons, for example, on molecules inthe electron transporting layer.

If a phosphorescent device having a triplet blocking layer satisfies thefollowing energy relationship:E^(T) _(d)<E^(T) _(TB)wherein E^(T) _(d) is the triplet energy of the phosphorescent dopant inthe light emitting layer and E^(T) _(TB) is the triplet energy of thecompound forming the triplet blocking layer,the triplet excitons of phosphorescent dopant are confined (not diffuseto other molecules). Therefore, the energy deactivation process otherthan the emission on the phosphorescent dopant may be prevented to causethe emission with high efficiency. However, even in case of satisfyingthe relationship of E^(T) _(d)<E^(T) _(TB), the triplet excitons maymove into other molecules if the energy difference (ΔE^(T)=E^(T)_(TB)−E^(T) _(d)) is small, because the energy difference ΔET may beovercome by the absorption of ambient heat energy when driving a deviceat around room temperature as generally employed in practical drive ofdevice. As compared with the fluorescent emission, the phosphorescentemission is relatively likely to be affected by the diffusion ofexcitons due to the heat absorption because the lifetime of tripletexcitons is longer. Therefore, as for the energy difference ΔE^(T), thelarger as compared with the heat energy of room temperature, the better.The energy difference ΔE^(T) is more preferably 0.1 eV or more andparticularly preferably 0.2 eV or more. In fluorescent devices, thematerial for organic EL device of the invention is usable as thematerial for triplet blocking layer of the TTF device described in WO2010/134350A1.

The electron mobility of the material for the triplet blocking layer ispreferably 10⁻⁶ cm²/Vs or more at an electric field strength in a rangeof 0.04 to 0.5 MV/cm. There are several methods for measuring theelectron mobility of organic material, for example, Time of Flightmethod. In the present invention, the electron mobility is determined byimpedance spectroscopy.

The electron mobility of the electron injecting layer is preferably 10⁻⁶cm²/Vs or more at an electric field strength in a range of 0.04 to 0.5MV/cm. Within the above range, the injection of electrons from thecathode to the electron transporting layer is promoted and the injectionof electrons to the adjacent blocking layer and light emitting layer isalso promoted, thereby enabling to drive a device at lower voltage.

EXAMPLES

The embodiments of the present invention will be described in moredetail with reference to the examples. However, it should be noted thatthe scope of the invention is not limited to the following examples.

Synthesis of Material for Organic EL Device Synthesis Example 1Synthesis of Intermediate 1

In argon stream, a mixture obtained by successively mixing2-nitro-1,4-dibromobenzene (11.2 g, 40 mmol), phenylboronic acid (4.9 g,40 mmol), tetrakis(triphenylphosphine)palladium (1.39 g, 1.2 mmol),toluene (120 mL), and a 2M aqueous solution of sodium carbonate (60 mL)was refluxed under heating for 8 h.

After cooling the reaction liquid to room temperature, the organic layerwas separated and the organic solvent was removed from the organic layerby distillation under reduced pressure. The obtained residue waspurified by a silica gel column chromatography to obtain theintermediate 1 (6.6 g, yield: 59%). The identification of theintermediate 1 was made by FD-MS (field desorption mass spectrometry)analysis.

Synthesis Example 2 Synthesis of Intermediate 2

In argon stream, a mixture obtained by successively mixing theintermediate 1 (6.6 g, 23.7 mmol), triphenylphosphine (15.6 g, 59.3mmol), and o-dichlorobenzene (24 mL) was heated at 180° C. for 8 h.

After cooling the reaction liquid to room temperature, the reactionproduct was purified by a silica gel column chromatography to obtain theintermediate 2 (4 g, yield: 68%). The identification of the intermediate2 was made by FD-MS analysis.

Synthesis Example 3 Synthesis of Intermediate 3

The procedure of Synthesis of Intermediate 1 was repeated except forusing the intermediate 2 in place of 2-nitro-1,4-dibromobenzene andusing 9-phenyl-9H-carbazole-3-ylboronic acid in place of phenylboronicacid. The obtained compound was identified as the intermediate 3 byFD-MS analysis.

Synthesis Example 4 Synthesis of Intermediate 4

The procedure of Synthesis of Intermediate 1 was repeated except forusing 3-bromocarbazole in place of 2-nitro-1,4-dibromobenzene and using9-phenyl-9H-carbazole-3-ylboronic acid in place of phenylboronic acid.

The obtained compound was identified as the intermediate 4 by FD-MSanalysis.

Synthesis Example 5 Synthesis of Intermediate 5

The procedure of Synthesis of Intermediate 1 was repeated except forusing 1-bromo-4-iodobenzene in place of 2-nitro-1,4-dibromobenzene andusing 9-phenyl-9H-carbazole-3-ylboronic acid in place of phenylboronicacid.

The obtained compound was identified as the intermediate 5 by FD-MSanalysis.

Synthesis Example 6 Synthesis of Intermediate 6

In argon stream, a mixture obtained by successively mixing theintermediate 5 (10 g, 25 mmol), bis(pinacolato)diboron (8.3 g, 33 mmol),dichloromethane adduct of[1,1′-bis(diphenylphosphino)ferrocene]palladium(II) dichloride (0.62 g,0.75 mmol), potassium acetate (7.4 g, 75 mmol), andN,N-dimethylformamide (170 mL) was refluxed under heating for 8 h.

After cooling the reaction liquid to room temperature, the organic layerwas separated and the organic solvent was removed from the organic layerby distillation under reduced pressure. The obtained residue waspurified by a silica gel column chromatography to obtain theintermediate 6 (10 g, yield: 91%). The identification of theintermediate 6 was made by FD-MS analysis.

Synthesis Example 7 Synthesis of Intermediate 7

The procedure of Synthesis of Intermediate 1 was repeated except forusing 3-bromocarbazole in place of 2-nitro-1,4-dibromobenzene and usingthe intermediate 6 in place of phenylboronic acid. The obtained compoundwas identified as the intermediate 7 by FD-MS analysis.

Synthesis Example 8 Synthesis of Intermediate 8

The procedure of Synthesis of Intermediate 1 was repeated except forusing 2,4,6-trichloropyrimidine in place of 2-nitro-1,4-dibromobenzene.The obtained compound was identified as the intermediate 8 by FD-MSanalysis.

Synthesis Example 9 Synthesis of Intermediate 9

The procedure of Synthesis of Intermediate 1 was repeated except forusing the intermediate 8 in place of 2-nitro-1,4-dibromobenzene andusing 4-cyanophenylboronic acid in place of phenylboronic acid. Theobtained compound was identified as the intermediate 9 by FD-MSanalysis.

Synthesis Example 10 Synthesis of Intermediate 10

The procedure of Synthesis of Intermediate 1 was repeated except forusing the intermediate 8 in place of 2-nitro-1,4-dibromobenzene andusing 3-cyanophenylboronic acid in place of phenylboronic acid. Theobtained compound was identified as the intermediate 10 by FD-MSanalysis.

Synthesis Example 11 Synthesis of Intermediate 11

The procedure of Synthesis of Intermediate 1 was repeated except forusing the intermediate 8 in place of 2-nitro-1,4-dibromobenzene andusing4′-(4,4,5,5-tetramethyl-1,3,2-dioxaborolane-2-yl)biphenyl-4-carbonitrilein place of phenylboronic acid. The obtained compound was identified asthe intermediate 11 by FD-MS analysis.

Synthesis Example 12 Synthesis of H1

In argon stream, a mixture obtained by successively mixing theintermediate 3 (4.1 g, 10 mmol), the intermediate 9 (3.5 g, 12 mmol),tris(dibenzylideneacetone)dipalladium (0.183 g, 0.20 mmol),tri-t-butylphosphonium tetrafluoroborate (0.15 g, 0.52 mmol), sodiumt-butoxide (1.9 g, 20 mmol), dry xylene (50 mL) was refluxed underheating for 8 h.

After cooling the reaction liquid to room temperature, the organic layerwas separated and the organic solvent was removed from the organic layerby distillation under reduced pressure. The obtained residue waspurified by a silica gel column chromatography to obtain 5.4 g ofyellowish white solid (H1).

The result of FD-MS measurement of the obtained compound is shown below.

FDMS: calcd for C₄₇H₂₉N₅=663. found m/z=663 (M+).

Synthesis Example 13 Synthesis of H2

The procedure of Synthesis of Compound H1 was repeated except for usingthe intermediate 4 in place of the intermediate 3.

The result of FD-MS measurement of the obtained compound is shown below.

FDMS: calcd for C₄₇H₂₉N₅=663, found m/z=663 (M+).

Synthesis Example 14 Synthesis of H3

The procedure of Synthesis of Compound H1 was repeated except for usingthe intermediate 10 in place of the intermediate 9.

The result of FD-MS measurement of the obtained compound is shown below.

FDMS: calcd for C₄₇H₂₉N₅=663, found m/z=663 (M+).

Synthesis Example 15 Synthesis of H4

The procedure of Synthesis of Compound H1 was repeated except for usingthe intermediate 7 in place of the intermediate 3 and using theintermediate 10 in place of the intermediate 9.

The result of FD-MS measurement of the obtained compound is shown below.

FDMS: calcd for C₅₃H₃₃N₅=739, found m/z=739 (M+).

Synthesis Example 16 Synthesis of H5

The procedure of Synthesis of Compound H1 was repeated except for usingthe intermediate 11 in place of the intermediate 9.

The result of FD-MS measurement of the obtained compound is shown below.

FDMS: calcd for C₅₃H₃₃N₅=739, found m/z=739 (M+).

Synthesis Example 17 Synthesis of Intermediate 12

In argon stream, a mixture obtained by successively mixing theintermediate 3 (7.0 g, 17 mmol), 1-bromo-4-iodobenzene (7.3 g, 26 mmol),copper iodide (228 mg, 1.2 mmol), potassium phosphate (5.4 g, 26 mmol),cyclohexanediamine (293 mg, 2.6 mmol), and dry dioxane (86 mL) wasstirred at 115° C. for 7 h.

The reaction liquid was cooled to room temperature and then filtered.The obtained solid was purified by a silica gel column chromatography toobtain the intermediate 12 (8.1 g, yield: 84%). The identification ofthe intermediate 12 was made by FD-MS analysis.

Synthesis Example 18 Synthesis of Intermediate 13

The procedure of Synthesis of Intermediate 6 was repeated except forusing the intermediate 12 in place of the intermediate 5. The obtainedcompound was identified as the intermediate 13 by FD-MS analysis.

Synthesis Example 19 Synthesis of H6

The procedure of Synthesis of Intermediate 1 was repeated except forusing 2-bromo-5-cyanopyridine in place of 2-nitro-1,4-dibromobenzene andusing the intermediate 13 in place of phenylboronic acid.

The result of FD-MS measurement of the obtained compound is shown below.

FDMS: calcd for C₄₂H₂₆N₄=586, found m/z=586 (M+).

Synthesis Example 20 Synthesis of Intermediate 14

The procedure of Synthesis of Intermediate 1 was repeated except forusing 5-bromo-2-chloropyrimidine in place of 2-nitro-1,4-dibromobenzeneand using 4-cyano phenylboronic acid in place of phenylboronic acid. Theobtained compound was identified as the intermediate 14 by FD-MSanalysis.

Synthesis Example 21 Synthesis of H7

The procedure of Synthesis of H1 was repeated except for using theintermediate 14 in place of the intermediate 9.

The result of FD-MS measurement of the obtained compound is shown below.

FDMS: calcd for C₄₁H₂₅N₅=587, found m/z=587 (M+).

Synthesis Example 22 Synthesis of Intermediate 15

In argon stream, a mixture of cyanuric chloride (20 g, 0.11 mol) and drytoluene (650 mL) was cooled on ice. After adding phenylmagnesium bromide(1 mol/L tetrahydrofuran solution) (108 mL, 0.11 mol) dropwise, themixture was stirred for 2 h.

After adding 1 N hydrochloric acid to the reaction liquid, thetemperature was returned to room temperature. The organic layer wasseparated and the organic solvent was removed by distillation underreduced pressure. The obtained residue was dissolved in methanol and thegenerated solid was collected by filtration and purified by washing withmethanol and hexane, to obtain the intermediate 15 (18 g, yield: 80%).The identification of the intermediate 15 was made by FD-MS analysis.

Synthesis Example 23 Synthesis of Intermediate 16

The procedure of Synthesis of Intermediate 1 was repeated except forusing the intermediate 15 in place of 2-nitro-1,4-dibromobenzene andusing4′-(4,4,5,5-tetramethyl-1,3,2-dioxaborolane-2-yl)biphenyl-4-carbonitrilein place of phenylboronic acid. The obtained compound was identified asthe intermediate 16 by FD-MS analysis.

Synthesis Example 24 Synthesis of H8

The procedure of Synthesis of Compound H1 was repeated except for usingthe intermediate 16 in place of the intermediate 9.

The result of FD-MS measurement of the obtained compound is shown below.

FDMS: calcd for C₅₂H₃₂N₆=740, found m/z=740 (M+).

Synthesis Example 25 Synthesis of Intermediate 17

The procedure of Synthesis of Intermediate 1 was repeated except forusing the intermediate 8 in place of 2-nitro-1,4-dibromobenzene andusing3′-(4,4,5,5-tetramethyl-1,3,2-dioxaborolane-2-yl)biphenyl-4-carbonitrilein place of phenylboronic acid. The obtained compound was identified asthe intermediate 17 by FD-MS analysis.

Synthesis Example 26 Synthesis of H9

The procedure of Synthesis of Compound H1 was repeated except for usingthe intermediate 17 in place of the intermediate 9.

The result of FD-MS measurement of the obtained compound is shown below.

FDMS: calcd for C₅₃H₃₃N₅=739, found m/z=739 (M+)

Production of Organic EL Device and Evaluation of Emission PerformanceExample 1

Production of Organic EL Device

A glass substrate of 25 mm×75 mm×1.1 mm thickness having an ITOtransparent electrode (product of Geomatec Company) was cleaned byultrasonic cleaning in isopropyl alcohol for 5 min and then UV ozonecleaning for 30 min.

The cleaned glass substrate was mounted to a substrate holder of avacuum vapor deposition apparatus. The electron accepting compound C-1(acceptor) shown below was vapor-deposited so as to cover thetransparent electrode to form a compound C-1 film with a thickness of 5nm. On the compound C-1 film, a first hole transporting material(aromatic amine derivative (compound X1) shown below) wasvapor-deposited to form a first hole transporting layer with a thicknessof 65 nm. Successively after forming the first hole transporting layer,a second hole transporting material (aromatic amine derivative (compoundX2) shown below) was vapor-deposited to form a second hole transportinglayer with a thickness of 10 nm.

On the second hole transporting layer, the compound H1 (host material)and Ir(bzq)₃ (phosphorescent emitting material) shown below wereco-deposited to form a phosphorescent light emitting layer with athickness of 25 nm. The concentration of Ir(bzq)₃ in the light emittinglayer was 10.0% by mass. The co-deposited film works as a light emittinglayer.

Successively after forming the light emitting layer, the compound ETshown below was vapor-deposited into a film with a thickness of 35 nm.The compound ET film works as an electron transporting layer.

Then, LiF was vapor-deposited into a film with a thickness of 1 nm at afilm-forming speed of 0.1 Å/min to form an electron injecting electrode(cathode). On the LiF film, metallic Al was vapor-deposited to form ametallic cathode with a thickness of 80 nm, thereby obtaining an organicEL device.

The obtained organic EL device was measured for the device performance(80% lifetime) by driving the device at current density of 50 mA/cm².The 80% lifetime is the time taken until the luminance was reduced to80% of the initial luminance when driving the device at constantcurrent. The result is shown in Table 1.

The compounds used in the examples and comparative examples are shownbelow.

Examples 2 to 3 and 5 and Comparative Example 1

Each organic EL device was produced in the same manner as in Example 1except for forming the light emitting layer by using the compound listedin Table 1 in place of the host compound H1.

The results of the measurement of device performance made in the samemanner as in Example 1 are shown in Table 1.

Example 4

An organic EL device was produced in the same manner as in Example 1except for forming the light emitting layer by using the compound H1 asthe host material 1 and the compound F1 as the host material 2 in placeof using only the compound H1. The concentration in the light emittinglayer was 10.0% by mass for Ir(bzq)₃, 45.0% by mass for the hostmaterial 1, and 45.0% by mass for the host material 2.

The results of the measurement of device performance made in the samemanner as in Example 1 are shown in Table 1.

Example 6

An organic EL device was produced in the same manner as in Example 4except for using the compound H5 as the host material 1 in place of thecompound H1

The results of the measurement of device performance made in the samemanner as in Example 1 are shown in Table 1.

TABLE 1 Light emitting layer 80% Host material 1 Host material 2Lifetime (h) Example 1 Compound H1 — 1600 Example 2 Compound H2 — 1600Example 3 Compound H3 — 600 Example 4 Compound H1 Compound F1 1200Example 5 Compound H5 — 600 Example 6 Compound H5 Compound F1 800Comparative Compound F1 — 350 Example 1

As seen from Table 1, as compared with the organic EL device ofComparative Example 1 which employed the compound F1 having a similarcentral skeleton but having no cyano-substituted group at its terminalend, the organic EL devices of Examples 1 to 3 and 5, wherein each ofthe compounds H1 to H3 and H5 each having a cyano-substituted azine ringat the terminal end of the central skeleton comprising the carbazolederivative was used as the host material of the light emitting layer,had longer lifetimes.

The organic EL devices of Examples 4 and 6, wherein the compound H1(material for organic EL device of the invention) and the compound F1having no cyano group were combinedly used as the host materials, alsohad longer 80% lifetimes.

Stability of Excited State

Preparation of Test Sample

On a glass substrate of 25 mm×75 mm×1.1 mm thickness, a transparentelectrode of indium tin oxide was formed. The resultant glass plate wasultrasonically cleaned in isopropyl alcohol and then cleaned underirradiation of ultraviolet light and ozone. The cleaned glass substratewith the transparent electrode was mounted to a substrate holder of adeposition chamber in a vacuum vapor deposition apparatus and thepressure in the deposition chamber was reduced to 1×10⁻³ Pa.

Then, the compound F1 was vapor-deposited at a deposition speed of 2nm/s so as to cover the transparent electrode, thereby forming a filmwith a thickness of 50 nm.

Then, aluminum was vapor-deposited at a deposition speed of 2 nm/s toform a reflecting electrode with a thickness of 100 nm.

Further, to prevent moisture adsorption, a protecting glass plate wasput on the electrode and sealed with an adhesive, thereby preparing atest sample A.

A test sample B was prepared in the same manner as above except forchanging the compound F1 to the compound H1.

Evaluation of Stability of Excited State Caused by UltravioletIrradiation

The test sample A was irradiated with ultraviolet light (365 nm, 850mW/cm²) from the side of the glass substrate with causing thetransparent electrode and the reflecting electrode a short circuit. Theultraviolet light passed through the transparent electrode was absorbedby the compound F1, to cause the excited state.

The measurement of the photoluminescence (PL) of the compound F1 in thetest sample A showed that the photoluminescence intensity was decreasedwith increasing cumulative time of ultraviolet irradiation. Thissuggests that the excited state of the compound F1 caused by ultravioletirradiation is unstable and the deterioration of the material lowers thefluorescent yield of the thin film made of the compound F1. Thecumulative time of ultraviolet irradiation taken until the PL intensityof the test sample A was reduced to 80% of the initial intensity was 10h.

The test sample B was also measured for the decrease with time of the PLintensity. To make the number of the excited molecules to be generatedby the ultraviolet irradiation equal to that of the test sample A, thetest sample B was irradiated with ultraviolet light at a radiationintensity of 770 mW/cm². The cumulative time of ultraviolet irradiationtaken until the PL intensity of the test sample B was reduced to 80% ofthe initial intensity was 72 h, this being 7 times as long as that ofthe test sample A.

These results show that the stability of the excited state of thecompound H1 of the invention is largely enhanced as compared with thecompound F1. Therefore, the lifetime of the device of Example 1 longerthan that of Comparative Example 1 is attributable to the prevention ofthe compound H1 in the device of Example 1 from being deteriorated,because the stability of the compound H1 is improved as compared withthe compound F1.

INDUSTRIAL APPLICABILITY

As described above in detail, the material for organic EL device of theinvention is useful as a material realizing an organic EL device withlong lifetime.

REFERENCE NUMERALS

-   1: Organic electroluminescence device-   2: Substrate-   3: Anode-   4: Cathode-   5: Phosphorescent light emitting layer-   6: Hole injecting/transporting layer-   7: Electron injecting/transporting layer-   10: Organic thin film layer

What is claimed is:
 1. A material for organic electroluminescence devicerepresented by formula (I);

wherein each of A¹ and A² independently represents a single bond, asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 30ring carbon atoms, or a substituted or unsubstituted heterocyclic grouphaving 5 to 30 ring atoms; each of X¹ to X⁸ and Y¹ to Y⁸ independentlyrepresents N (nitrogen atom) or CR^(a) (C represents a carbon atom);each of R^(a) independently represents a hydrogen atom, a substituted orunsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms, a substituted or unsubstituted heterocyclic group having 5 to 30ring atoms, a substituted or unsubstituted alkyl group having 1 to 30carbon atoms, a substituted or unsubstituted silyl group, or a halogenatom, provided that when two or more R^(a) groups exist, the R^(a)groups may be the same or different; L¹ represents a single bond, asubstituted or unsubstituted divalent aromatic hydrocarbon group having6 to 30 ring carbon atoms, or a substituted or unsubstituted divalentheterocyclic group having 5 to 30 ring atoms; n represents an integer of0 to 3, provided that when n=0, L¹ represents a single bond and one ofX⁵ to X⁸ and one of Y¹ to Y⁸ and A² are directly bonded to each other;one of X⁵ to X⁸ and one of Y¹ to Y⁸ and A² are bonded to each other viaL¹ or directly; each of sa and ta independently represents an integer of0 to 5, each of sb, tb and tc independently represents an integer of 0to 4, and sc represents an integer of 0 to 3, provided thatsa+sb+sc+ta+tb+tc represents an integer of 1 to 5; when sa is 1 to 5, A¹and Q¹ of (Q¹)_(sa) are bonded to each other; when sb is 1 to 4, atleast one of X¹ to X⁴ and Q¹ of (Q¹)_(sb) are bonded to each other; whensc is 1 to 3, at least one of X⁵ to X⁸ and Q¹ of (Q¹)_(sc) are bonded toeach other; when ta is 1 to 5, A² and Q² of (Q²)_(ta) are bonded to eachother; when tb is 1 to 4, at least one of Y⁵ to Y⁸ and Q² of (Q²)_(tb)are bonded to each other; when tc is 1 to 4, at least one of Y¹ to Y⁴and Q² of (Q²)_(tc) are bonded to each other; each of Q¹ and Q²independently represents -Az-W_(q); q represents an integer of 1 to 4;when two or more Q¹ groups exist, the Q¹ groups may be the same ordifferent; when two or more Q² groups exist, the Q² groups may be thesame or different; Az represents a q+1 valent residue of a ringrepresented by formula (X):

wherein each of Z¹ to Z⁵ independently represents a nitrogen atom orCR^(b); R^(b) is as defined in R^(a), provided that when any two of Z¹to Z⁵ adjacent to each other represent CR^(b), the adjacent R^(b) groupsmay be bonded to each other to form a ring structure; when two or moreR^(b) groups exist, the R^(b) groups may be the same or different; whentwo or more Az groups exist, the Az groups may be the same or different;W represents a cyano group, a cyano-substituted aromatic hydrocarbongroup having 6 to 30 ring carbon atoms, or a cyano-substitutedheterocyclic group having 5 to 30 ring atoms, provided that thecyano-substituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms and the cyano-substituted heterocyclic group having 5 to 30 ringatoms may be further substituted by a substituent other than a cyanogroup, and when two or more W groups exist, the W groups may be the sameor different.
 2. The material for organic electroluminescence deviceaccording to claim 1, represented by formula (II):

wherein A¹, A², X¹ to X⁸, Y¹ to Y⁸, L¹, n, sa, sb, sc, ta, tb, Q¹, andQ² are as defined above, tc represents an integer of 0 to 3, providedthat sa+sb+sc+ta+tb+tc represents an integer of 1 to 5; and one of X⁵ toX⁸ and one of Y¹ to Y⁴ are bonded to each other via L¹ or directly. 3.The material for organic electroluminescence device according to claim1, represented by formula (III):

wherein A¹, A², X¹ to X⁸, Y¹ to Y⁸, L¹, n, Q¹, and Q² are as definedabove; each of sa and ta independently represents an integer of 0 to 5,provided that sa+ta represents an integer of 1 to 5; and one of X⁵ to X⁸and one of Y¹ to Y⁴ are bonded to each other via L¹ or directly.
 4. Thematerial for organic electroluminescence device according to claim 1,wherein X⁷ and Y³ are bonded to each other via L¹ or directly.
 5. Thematerial for organic electroluminescence device according to claim 1,wherein X⁶ and Y² are bonded to each other via L¹ or directly.
 6. Thematerial for organic electroluminescence device according to claim 1,wherein X⁶ and Y³ are bonded to each other via L¹ or directly.
 7. Thematerial for organic electroluminescence device according to claim 1,wherein Az represents a q+1 valent residue of a ring selected from thegroup consisting of a substituted or unsubstituted pyrimidine ring, asubstituted or unsubstituted triazine ring, a substituted orunsubstituted pyridine ring, and a substituted or unsubstitutedquinazoline ring.
 8. The material for organic electroluminescence deviceaccording to claim 1, wherein L¹ represents a phenylene group and nrepresents an integer of 1 to 3, or L¹ represents a single bond and nrepresents
 0. 9. The material for organic electroluminescence deviceaccording to claim 1, wherein W represents a cyano-substituted phenylgroup, a cyano-substituted biphenyl group, a cyano-substituted9,9-diphenylfluorenyl group, a cyano-substituted9,9′-spirobi[9H-fluorene]-2-yl group, a cyano-substituted9,9-dimethylfluorenyl group, a cyano-substituted dibenzofuranyl group,or a cyano-substituted dibenzothiophenyl group.
 10. The material fororganic electroluminescence device according to claim 1, wherein each ofsa, sb, sc, ta, tb, and tc represents 0 or
 1. 11. The material fororganic electroluminescence device according to claim 1, wherein each ofta, tb and tc represents
 0. 12. The material for organicelectroluminescence device according to claim 1, whereinsa+sb+sc+ta+tb+tc represents
 1. 13. The material for organicelectroluminescence device according to claim 1, wherein q represents 1or
 2. 14. The material for organic electroluminescence device accordingto claim 1, wherein q represents
 1. 15. An organic electroluminescencedevice comprising an organic thin film layer comprising one or morelayers between a cathode and an anode, wherein the organic thin filmlayer comprises a light emitting layer, and at least one layer of theorganic thin film layer comprises the material for organicelectroluminescence device according to claim
 1. 16. The organicelectroluminescence device according to claim 15, wherein the lightemitting layer comprises the material for organic electroluminescencedevice.
 17. The organic electroluminescence device according to claim15, wherein the light emitting layer comprises a phosphorescent emittingmaterial selected from ortho metallated complexes of a metal selectedfrom iridium (Ir), osmium (Os), and platinum (Pt).
 18. The organicelectroluminescence device according to claim 15, wherein the lightemitting layer comprises a first host material selected from thematerial for organic electroluminescence device and a second hostmaterial represented by formula (1);

wherein Z¹¹ represents a ring structure fused to a side a andrepresented by formula (1-1) or (1-2), and Z¹² represents a ringstructure fused to a side b and represented by formula (1-1) or (1-2),provided that at least one of Z¹¹ and Z¹² is represented by formula(1-1);

in formula (1-1), a side c is fused to the side a or b of formula (1);in formula (1-2), any one of sides d, e and f is fused to the side a orb of formula (1); in formulae (1-1) and (1-2), X¹¹ represents a sulfuratom, an oxygen atom, N—R¹⁹, or C(R²⁰)(R²¹); each of R¹¹ to R²¹independently represents a hydrogen atom, a heavy hydrogen atom, ahalogen atom, a cyano group, a substituted or unsubstituted aromatichydrocarbon group having 6 to 30 ring carbon atoms, a substituted orunsubstituted heterocyclic group having 5 to 30 ring atoms, asubstituted or unsubstituted alkyl group having 1 to 30 carbon atoms, asubstituted or unsubstituted alkenyl group having 2 to 30 carbon atoms,a substituted or unsubstituted alkynyl group having 2 to 30 carbonatoms, a substituted or unsubstituted alkylsilyl group having 3 to 30carbon atoms, a substituted or unsubstituted arylsilyl group having 6 to30 ring carbon atoms, a substituted or unsubstituted alkoxy group having1 to 30 carbon atoms, a substituted or unsubstituted aralkyl grouphaving 6 to 30 ring carbon atoms, or a substituted or unsubstitutedaryloxy group having 6 to 30 ring carbon atoms, provided that adjacentgroups of R¹¹ to R²¹ may be bonded to each other to form a ring; M¹represent a substituted or unsubstituted nitrogen-containing aromaticheteroring having 5 to 30 ring atoms; L² represents a single bond, asubstituted or unsubstituted divalent aromatic hydrocarbon group having6 to 30 ring carbon atoms, a substituted or unsubstituted divalentheterocyclic group having 5 to 30 ring atoms, a cycloalkylene grouphaving 5 to 30 ring atoms, or a group in which the preceding groups aredirectly linked to each other; and k represents 1 or
 2. 19. The organicelectroluminescence device according to claim 18, wherein the secondhost material is represented by formula (2):

wherein Z¹¹ represents a ring structure fused to the side a andrepresented by formula (1-1) or (1-2), and Z¹² represents a ringstructure fused to the side b and represented by formula (1-1) or (1-2),provided that at least one of Z¹¹ and Z¹² is represented by formula(1-1); L² is as defined in formula (1); each of X¹² to X¹⁴ independentlyrepresents a nitrogen atom, CH, or a carbon atom bonded to R³¹ or L²,provided that at least one of X¹² to X¹⁴ represents a nitrogen atom;each of Y¹¹ to Y¹³ independently represents CH or a carbon atom bondedto R³¹ or L²; each of R³¹ independently represents a halogen atom, acyano group, a substituted or unsubstituted aromatic hydrocarbon grouphaving 6 to 30 ring carbon atoms, a substituted or unsubstitutedheterocyclic group having 5 to 30 ring atoms, a substituted orunsubstituted alkyl group having 1 to 30 carbon atoms, a substituted orunsubstituted alkenyl group having 2 to 30 carbon atoms, a substitutedor unsubstituted alkynyl group having 2 to 30 carbon atoms, asubstituted or unsubstituted alkylsilyl group having 3 to 30 carbonatoms, a substituted or unsubstituted arylsilyl group having 6 to 30ring carbon atoms, a substituted or unsubstituted alkoxy group having 1to 30 carbon atoms, a substituted or unsubstituted aralkyl group having6 to 30 ring carbon atoms, or a substituted or unsubstituted aryloxygroup having 6 to 30 ring carbon atoms; when two or more R³¹ groupsexist, the R³¹ groups may be the same or different and adjacent R³⁴groups may be bonded to each other to form a ring; k represents 1 or 2,and m represents an integer of 0 to 4; the side c of formula (1-1) isfused to the side a or b of formula (2); and any one of sides d, e and fof formula (1-2) is fused to the side a or b of formula (2).
 20. Theorganic electroluminescence device according to claim 18, wherein thesecond host material is represented by formula (3):

wherein L² is as defined in formula (1); each of X¹² to X¹⁴independently represents a nitrogen atom, CH, or a carbon atom bonded toR³¹ or L², provided that at least one of X¹² to X¹⁴ represents anitrogen atom; each of Y¹¹ to Y¹³ independently represents CH or acarbon atom bonded to R³¹ or L²; each of R³¹ independently represents ahalogen atom, a cyano group, a substituted or unsubstituted aromatichydrocarbon group having 6 to 30 ring carbon atoms, a substituted orunsubstituted heterocyclic group having 5 to 30 ring atoms, asubstituted or unsubstituted alkyl group having 1 to 30 carbon atoms, asubstituted or unsubstituted alkenyl group having 2 to 30 carbon atoms,a substituted or unsubstituted alkynyl group having 2 to 30 carbonatoms, a substituted or unsubstituted alkylsilyl group having 3 to 30carbon atoms, a substituted or unsubstituted arylsilyl group having 6 to30 ring carbon atoms, a substituted or unsubstituted alkoxy group having1 to 30 carbon atoms, a substituted or unsubstituted aralkyl grouphaving 6 to 30 ring carbon atoms, or a substituted or unsubstitutedaryloxy group having 6 to 30 ring carbon atoms; when two or more R³¹groups exist, the R³¹ groups may be the same or different and adjacentR³¹ groups may be bonded to each other to form a ring; m represents aninteger of 0 to 4; each of R⁴¹ to R⁴⁸ independently represents ahydrogen atom, a heavy hydrogen atom, a halogen atom, a cyano group, asubstituted or unsubstituted aromatic hydrocarbon group having 6 to 30ring carbon atoms, a substituted or unsubstituted heterocyclic grouphaving 5 to 30 ring atoms, a substituted or unsubstituted alkyl grouphaving 1 to 30 carbon atoms, a substituted or unsubstituted alkenylgroup having 2 to 30 carbon atoms, a substituted or unsubstitutedalkynyl group having 2 to 30 carbon atoms, a substituted orunsubstituted alkylsilyl group having 3 to 30 carbon atoms, asubstituted or unsubstituted arylsilyl group having 6 to 30 ring carbonatoms, a substituted or unsubstituted alkoxy group having 1 to 30 carbonatoms, a substituted or unsubstituted aralkyl group having 6 to 30 ringcarbon atoms, or a substituted or unsubstituted aryloxy group having 6to 30 ring carbon atoms; and adjacent groups of R⁴¹ to R⁴⁸ may be bondedto each other to form a ring.
 21. The organic electroluminescence deviceaccording to claim 18, wherein the second host material is representedby formula (4):

wherein L² is as defined in formula (1); each of X¹² to X¹⁴independently represents a nitrogen atom, CH, or a carbon atom bonded toR³¹ or L², provided that at least one of X¹² to X¹⁴ represents anitrogen atom; each of Y¹¹ to Y¹³ independently represents CH or acarbon atom bonded to R³¹ or L²; each of R³¹ independently represents ahalogen atom, a cyano group, a substituted or unsubstituted aromatichydrocarbon group having 6 to 30 ring carbon atoms, a substituted orunsubstituted heterocyclic group having 5 to 30 ring atoms, asubstituted or unsubstituted alkyl group having 1 to 30 carbon atoms, asubstituted or unsubstituted alkenyl group having 2 to 30 carbon atoms,a substituted or unsubstituted alkynyl group having 2 to 30 carbonatoms, a substituted or unsubstituted alkylsilyl group having 3 to 30carbon atoms, a substituted or unsubstituted arylsilyl group having 6 to30 ring carbon atoms, a substituted or unsubstituted alkoxy group having1 to 30 carbon atoms, a substituted or unsubstituted aralkyl grouphaving 6 to 30 ring carbon atoms, or a substituted or unsubstitutedaryloxy group having 6 to 30 ring carbon atoms; when two or more R³¹groups exist, the R³¹ groups may be the same or different and adjacentR³¹ groups may be bonded to each other to form a ring; m represents aninteger of 0 to 4; each of L³ and L⁴ independently represents a singlebond, a substituted or unsubstituted divalent aromatic hydrocarbon grouphaving 6 to 30 ring carbon atoms, a substituted or unsubstituteddivalent heterocyclic group having 5 to 30 ring atoms, a cycloalkylenegroup having 5 to 30 ring atoms, or a group in which the precedinggroups are directly linked to each other; each of R⁵¹ to R⁵⁴independently represents a halogen atom, a cyano group, a substituted orunsubstituted aromatic hydrocarbon group having 6 to 30 ring carbonatoms, a substituted or unsubstituted heterocyclic group having 5 to 30ring atoms, a substituted or unsubstituted alkyl group having 1 to 30carbon atoms, a substituted or unsubstituted alkenyl group having 2 to30 carbon atoms, a substituted or unsubstituted alkynyl group having 2to 30 carbon atoms, a substituted or unsubstituted alkylsilyl grouphaving 3 to 30 carbon atoms, a substituted or unsubstituted arylsilylgroup having 6 to 30 ring carbon atoms, a substituted or unsubstitutedalkoxy group having 1 to 30 carbon atoms, a substituted or unsubstitutedaralkyl group having 6 to 30 ring carbon atoms, or a substituted orunsubstituted aryloxy group having 6 to 30 ring carbon atoms; when twoor more R⁵¹ groups exist, the R⁵¹ groups may be the same or differentand adjacent R⁵¹ groups may be bonded to each other to form a ring; whentwo or more R⁵² groups exist, the R⁵² groups may be the same ordifferent and adjacent R⁵² groups may be bonded to each other to form aring; when two or more R⁵³ groups exist, the R⁵³ groups may be the sameor different and adjacent R⁵³ groups may be bonded to each other to forma ring; when two or more R⁵⁴ groups exist, the R⁵⁴ groups may be thesame or different and adjacent R⁵⁴ groups may be bonded to each other toform a ring; M² represents a substituted or unsubstituted aromatichydrocarbon group having 6 to 30 ring carbon atoms or a substituted orunsubstituted heterocyclic group having 5 to 30 ring atoms; and each ofp and s independently represents an integer of 0 to 4, and each of q andr independently represents an integer of 0 to
 3. 22. The organicelectroluminescence device according to claim 15, wherein the lightemitting layer comprises a first host material selected from thematerials for organic electroluminescence device and a second hostmaterial selected from compounds having no cyano group.